Methods and apparatus for sidelink communications and resource allocation

ABSTRACT

Methods and systems are provided in which a UE transmits sidelink (SL) control information comprising a scheduling assignment (SA) indicating an SL transmission resource for a SL data transmission to a target UE. The SL transmission resource is based on one or more occupied SL resources identified by the UE and the SL transmission resource includes resources for an initial transmission and one or more retransmissions. The UE then transmits the SL data transmission using the SL transmission resource according to the transmitted SL control information. This is done without receiving, in a downlink control information (DCI), a grant of communication resources.

RELATED APPLICATION

This application claims the benefit of U.S. provisional application No.62/755,392 filed Nov. 2, 2018, and hereby incorporated by reference inits entirety. This application is related to U.S. provisionalapplication No. 62/665,286 filed May 1, 2018, and hereby incorporated byreference in its entirety.

FIELD

The application relates generally to wireless sidelink (SL)communications, and in particular embodiments, to resource allocationthereof.

BACKGROUND

One possible application of sidelink (SL) communications is vehicle toeverything/anything (V2X) communication, for example, which is anincreasingly important new category of communication that may becomewidespread in next generation wireless communication networks, such as5G New Radio (NR) systems. V2X refers to a category of communicationscenarios, including communication from a vehicle to another vehicle(V2V), vehicle to infrastructure (V2I), and vehicle to pedestrian (V2P),for example. In general, a vehicle communicating in a network isconsidered user equipment (UE).

The communication in V2X systems may be performed using links betweenthe network and the UE, such as an uplink (UL) and a downlink (DL). TheUL is a wireless communication from a UE to a base station (BS), and theDL is a wireless communication from a BS to a UE. In V2V communicationusing the UL and DL, data is transmitted from a transmitting UE to a BS,and then transmitted from the BS to a receiving UE.

Alternatively, some of the V2X communication scenarios may be D2Dcommunications, in which case the transmission in V2X systems may beperformed between the transmitting UE and receiving UE using a sidelink.The SL allows data to be transmitted directly from the transmitting UEto the receiving UE, without forwarding the data via the BS.

Communication resources are required for UL, DL and SL communications.For example, a UE could wirelessly transmit data to or receive data fromanother UE using a particular frequency resource(s), and during aparticular time duration (e.g. slot, mini-slot, etc). The combination offrequency and time slot define a communication resource in this example.

Challenges in V2X communications, and more generally SL communications,include efficient communication resource allocation and usage by UEs.

Furthermore, the SL also enables UE cooperation, which may be used toenhance the reliability, throughput, and capacity of communications. Forexample, data from a BS intended for a target UE (TUE) may be firsttransmitted to a cooperating UE (CUE), and then forwarded to the TUE.Similarly, data from the TUE intended for the BS may be forwarded viathe CUE.

In general, the SL and UE cooperation may enhance the reliability,throughput, and capacity of any wireless communications. However,successful UE cooperation requires proper management of the SL betweenCUEs and TUEs in order to reduce interference and improve UE cooperationbenefits.

The present disclosure relates to a new mode of SL communication, whichmay be particularly suitable for V2X scenarios, but could be used inother applications. In particular, the new mode of SL communication mayenable SL transmissions that do not necessitate a corresponding dynamicscheduling of physical communication resources. In other words, the newmode of SL communication may enable UEs to perform communications in anautonomous manner, without necessitating dynamic control from a basestation, yet also without the common drawbacks associated withconventional autonomous SL communications.

SUMMARY

According to one aspect of the present disclosure, there is provided amethod performed by a user equipment (UE), the method comprising:transmitting sidelink (SL) control information comprising a schedulingassignment (SA) indicating an SL transmission resource for a SL datatransmission to a target UE, the SL transmission resource based on oneor more occupied SL resources identified by the UE, and the SLtransmission resource including resources for an initial transmissionand one or more retransmissions; and transmitting the SL datatransmission using the SL transmission resource according to thetransmitted SL control information, wherein the SL control informationand the SL data communication are transmitted by the UE withoutreceiving, in a downlink control information (DCI), a grant ofcommunication resources.

Optionally, the method further comprises sensing a SL transmissioninvolving another UE to identify the one or more occupied SL resources.

Optionally, sensing the SL transmission involving the another UEcomprises decoding a sidelink control channel transmitted by the anotherUE to identify a transmission resource scheduled for the another UE.

Optionally, decoding the SL control channel transmitted by the anotherUE comprises decoding one or a combination of: a scheduling assignment;a side link control information (SCI); and a physical sidelink controlchannel (PSCCH).

Optionally, the method further comprises selecting the SL transmissionresource by avoiding selecting the transmission resource scheduled forthe another UE.

Optionally, the same resources are selected for the initial transmissionand the one or more retransmissions.

Optionally, the SL transmission resource comprises a SL transmissionpattern, the transmission resource scheduled for the another UEcomprises a transmission pattern scheduled for the another UE, andavoiding selecting the transmission resource scheduled for the anotherUE comprises avoiding the transmission pattern scheduled for the anotherUE.

Optionally, sensing the SL transmission involving the another UEcomprises measuring SL transmission resources.

Optionally, measuring SL transmission resources comprises measuringphysical sidelink shared channel (PSSCH) resources indicated or reservedfor transmission by a sidelink control information transmitted by theanother UE.

Optionally, the initial transmission and the one or more retransmissionscorrespond to a same transport block or different transport blocks.

According to another aspect of the present invention, there is provideda user equipment comprising: a processor; and a non-transitory computerreadable storage medium storing programming for execution by theprocessor, the programming including instructions for: transmittingsidelink (SL) control information comprising a scheduling assignment(SA) indicating an SL transmission resource for a SL data transmissionto a target UE, the SL transmission resource based on one or moreoccupied SL resources identified by the UE, and the SL transmissionresource including resources for an initial transmission and one or moreretransmissions; and transmitting the SL data transmission using the SLtransmission resource according to the transmitted SL controlinformation, wherein the SL control information and the SL datacommunication are transmitted by the UE without receiving, in a downlinkcontrol information (DCI), a grant of communication resources.

Optionally, the programming further includes instructions for sensing aSL transmission involving another UE to identify the one or moreoccupied SL resources.

Optionally, sensing the SL transmission involving the another UEcomprises decoding a sidelink control channel transmitted by the anotherUE to identify a transmission resource scheduled for the another UE.

Optionally, decoding the SL control channel transmitted by the anotherUE comprises decoding one or a combination of: a scheduling assignment;a side link control information (SCI); and a physical sidelink controlchannel (PSCCH).

Optionally, the programming further includes instructions for selectingthe SL transmission resource by avoiding selecting the transmissionresource scheduled for the another UE.

Optionally, the same resources are selected for the initial transmissionand the one or more retransmissions.

Optionally, the SL transmission resource comprises a SL transmissionpattern, the transmission resource scheduled for the another UEcomprises a transmission pattern scheduled for the another UE, andavoiding selecting the transmission resource scheduled for the anotherUE comprises avoiding the transmission pattern scheduled for the anotherUE.

Optionally, the SL transmission involving the another UE comprisesmeasuring SL transmission resources.

Optionally, measuring SL transmission resources comprises measuringphysical sidelink shared channel (PSSCH) resources indicated or reservedfor transmission by a sidelink control information transmitted by theanother UE.

Optionally, the initial transmission and the one or more retransmissionscorrespond to a same transport block or different transport blocks.

According to one aspect of the present disclosure, there is provided amethod performed by a user equipment (UE), the method comprising:decoding a sidelink (SL) control channel transmitted by another UE toascertain SL control information transmitted by the another UE;selecting a SL transmission resource for use in making a SL transmissionto a target UE taking into account the ascertained SL controlinformation; transmitting, by the UE, SL control information comprisinga scheduling assignment (SA) indicating the selected transmissionresource; and transmitting, by the UE, an SL data communicationaccording to the transmitted SL control information using the selectedSL transmission resource, wherein the SL control information and the SLdata communication are transmitted by the UE without receiving, in adownlink control information (DCI), a grant of communication resources.

Optionally, decoding a SL control channel transmitted by another UEcomprises decoding one or a combination of: scheduling assignment; sidelink control information (SCI); physical sidelink control channel(PSCCH); to determine transmission resources being scheduled by theanother UE.

Optionally, selecting a SL transmission resource for use in making a SLtransmission to a target UE taking into account the ascertained SLcontrol information comprises avoiding selecting a transmission resourcealready scheduled by another UE.

Optionally, each transmission resources comprises a transmissionpattern, and avoiding selecting the transmission resource alreadyscheduled by another UE comprises avoiding a transmission patternalready scheduled by another UE.

According to another aspect of the present disclosure, there is provideda method performed by a user equipment (UE), the method comprising:measuring sidelink (SL) transmission resources; selecting a SLtransmission resource for use in making a SL transmission to a target UEtaking into account the measurements; transmitting, by the UE, SLcontrol information comprising a scheduling assignment (SA) indicatingthe selected SL transmission resource; and transmitting, by the UE, anSL data communication according to the transmitted SL controlinformation using the selected SL transmission resource, wherein the SLcontrol information and the SL data communication are transmitted by theUE without receiving, in a downlink control information (DCI), a grantof communication resources.

Optionally, the method further comprises: measuring SL transmissionresources at different time instances; and averaging the different SLtransmission resource measurements.

Optionally, the method further comprises: determining a metric inrespect of each SL transmission resource based on the measurements overa window of time prior to data transmission; wherein selecting the SLtransmission resource comprises disqualifying at least one SLtransmission resource from selection based on the determined metrics.

Optionally, the method further comprises: determining a metric inrespect of each SL transmission resource based on the measurements overa window of time prior to data transmission; wherein selecting the SLtransmission resource comprises ordering the transmission resourcesbased on the metric.

Optionally, performing measurements on SL transmission resources on along-term basis prior to a sidelink transmission comprises measuring atleast one of: reference signal receive power (RSRP); and referencesignal receive quality (RSRQ).

Optionally, measuring the SL transmission resources comprises measuringenergy levels across one or more frequency bands at a first timeinstance.

Optionally, the method further comprises: performing a clear channelassessment (CCA) by comparing the measured energy levels to a specifiedthreshold.

Optionally, performing measurements on SL transmission resources at afirst time instance comprises: performing a measurement for a first SLtransmission resource; when the measurement indicates the first SLtransmission resource is being used, selecting a different SLtransmission resource as the selected SL transmission resource; and whenthe short-term measurement indicates the first SL transmission resourceis not being used, selecting the first SL transmission resource as theselected SL transmission resource.

Optionally, performing measurements on SL transmission resources at afirst time instance prior to a sidelink transmission comprisesperforming the measurement for a plurality of SL transmission resourcesand determining which of the plurality of SL transmission resources arenot being used for a current transmission period; and selecting a SLtransmission resource for use in making a SL transmission to a target UEtaking into account the measurements comprises selecting between the SLtransmission resources that are determined not being used for thecurrent transmission period.

According to another aspect of the present disclosure, there is provideda method comprising: decoding a sidelink (SL) control channeltransmitted by another UE to ascertain SL control informationtransmitted by the another UE and/or performing measurements on sidelink(SL) transmission resources; adaptively adjusting a SL transmissionresource for SL transmission based on the decoding of the SL controlchannel and/or measurements on SL transmission resources; transmitting,by the UE, SL control information indicating the adaptively adjusted SLtransmission resource; and transmitting, by the UE, an SL datacommunication using the adaptively adjusted SL transmission resource,wherein the SL control information and the SL data communication aretransmitted by the UE without receiving, in a downlink controlinformation (DCI), a grant of communication resources.

Optionally, adaptively adjusting a transmission SL resource comprisesadjusting one or a combination of: a number of repetitions; a size of atransmission pattern; and a location of a transmission pattern.

According to another aspect of the present disclosure, there is provideda method comprising: adaptively selecting between at least two sidelink(SL) communication resource configurations to be used by the UE for SLtransmissions; selecting a SL transmission resource for use in making aSL transmission to a target UE based on the selected SL communicationresource configuration; transmitting, by the UE, SL control informationaccording to the SL communication resource configuration; andtransmitting, by the UE, an SL data communication according to the SLcommunication resource configuration, wherein the SL control informationand the SL data communication are transmitted by the UE withoutreceiving, in a downlink control information (DCI), a grant ofcommunication resources.

Optionally, adaptively selecting between at least two sidelink (SL)communication resource configurations to be used by the UE for SLtransmissions is based on one or a combination of two or more of:traffic type, packet size, reliability target, latency target.

Optionally, sidelink control information comprises a resource allocationand power level for a sidelink transmission.

According to another aspect of the present disclosure, there is provideda user equipment (UE) comprising: a processor; and a non-transitorycomputer readable storage medium storing programming for execution bythe processor, the programming including instructions for: decoding asidelink (SL) control channel transmitted by another UE to ascertain SLcontrol information transmitted by the another UE; selecting a SLtransmission resource for use in making a SL transmission to a target UEtaking into account the ascertained SL control information;transmitting, by the UE, SL control information comprising a schedulingassignment (SA) indicating the selected transmission resource; andtransmitting, by the UE, an SL data communication according to thetransmitted SL control information using the selected SL transmissionresource, wherein the SL control information and the SL datacommunication are transmitted by the UE without receiving, in a downlinkcontrol information (DCI), a grant of communication resources.

Optionally, decoding a SL control channel transmitted by another UEcomprises decoding one or a combination of: scheduling assignment; sidelink control information (SCI); physical sidelink control channel(PSCCH); to determine transmission resources being scheduled by theanother UE.

Optionally, selecting a SL transmission resource for use in making a SLtransmission to a target UE taking into account the ascertained SLcontrol information comprises avoiding selecting a transmission resourcealready scheduled by another UE.

Optionally, each transmission resources comprises a transmissionpattern, and avoiding selecting the transmission resource alreadyscheduled by another UE comprises avoiding a transmission patternalready scheduled by another UE.

According to another aspect of the present disclosure, there is provideda user equipment (UE) comprising: a processor; and a non-transitorycomputer readable storage medium storing programming for execution bythe processor, the programming including instructions for: measuringsidelink (SL) transmission resources; selecting a SL transmissionresource for use in making a SL transmission to a target UE taking intoaccount the measurements; transmitting, by the UE, SL controlinformation comprising a scheduling assignment (SA) indicating theselected SL transmission resource; and transmitting, by the UE, an SLdata communication according to the transmitted SL control informationusing the selected SL transmission resource, wherein the SL controlinformation and the SL data communication are transmitted by the UEwithout receiving, in a downlink control information (DCI), a grant ofcommunication resources.

Optionally, the programming further including instructions for:measuring SL transmission resources at different time instances; andaveraging the different SL transmission resource measurements.

Optionally, the programming further including instructions for:determining a metric in respect of each SL transmission resource basedon the measurements over a window of time prior to data transmission;wherein selecting the SL transmission resource comprises disqualifyingat least one SL transmission resource from selection based on thedetermined metrics.

Optionally, the programming further including instructions for:determining a metric in respect of each SL transmission resource basedon the measurements over a window of time prior to data transmission;wherein selecting the SL transmission resource comprises ordering thetransmission resources based on the metric.

Optionally, performing measurements on SL transmission resources on along-term basis prior to a sidelink transmission comprises measuring atleast one of: reference signal receive power (RSRP); and referencesignal receive quality (RSRQ).

Optionally, measuring the SL transmission resources comprises measuringenergy levels across one or more frequency bands at a first timeinstance.

Optionally, the programming further including instructions for:performing a clear channel assessment (CCA) by comparing the measuredenergy levels to a specified threshold.

Optionally, performing measurements on SL transmission resources at afirst time instance comprises: performing a measurement for a first SLtransmission resource; when the measurement indicates the first SLtransmission resource is being used, selecting a different SLtransmission resource as the selected SL transmission resource; and whenthe short-term measurement indicates the first SL transmission resourceis not being used, selecting the first SL transmission resource as theselected SL transmission resource.

Optionally, performing measurements on SL transmission resources at afirst time instance prior to a sidelink transmission comprisesperforming the measurement for a plurality of SL transmission resourcesand determining which of the plurality of SL transmission resources arenot being used for a current transmission period; and selecting a SLtransmission resource for use in making a SL transmission to a target UEtaking into account the measurements comprises selecting between the SLtransmission resources that are determined not being used for thecurrent transmission period.

According to another aspect of the present disclosure, there is provideda user equipment (UE) comprising: a processor; and a non-transitorycomputer readable storage medium storing programming for execution bythe processor, the programming including instructions for: decoding asidelink (SL) control channel transmitted by another UE to ascertain SLcontrol information transmitted by the another UE and/or performingmeasurements on sidelink (SL) transmission resources; adaptivelyadjusting a SL transmission resource for SL transmission based on thedecoding of the SL control channel and/or measurements on SLtransmission resources; transmitting, by the UE, SL control informationindicating the adaptively adjusted SL transmission resource; andtransmitting, by the UE, an SL data communication using the adaptivelyadjusted SL transmission resource, wherein the SL control informationand the SL data communication are transmitted by the UE withoutreceiving, in a downlink control information (DCI), a grant ofcommunication resources.

Optionally, adaptively adjusting a transmission SL resource comprisesadjusting one or a combination of: a number of repetitions; a size of atransmission pattern; and a location of a transmission pattern.

According to another aspect of the present disclosure, there is provideda method comprising: adaptively selecting between at least two sidelink(SL) communication resource configurations to be used by the UE for SLtransmissions; selecting a SL transmission resource for use in making aSL transmission to a target UE based on the selected SL communicationresource configuration; transmitting, by the UE, SL control informationaccording to the SL communication resource configuration; andtransmitting, by the UE, an SL data communication according to the SLcommunication resource configuration, wherein the SL control informationand the SL data communication are transmitted by the UE withoutreceiving, in a downlink control information (DCI), a grant ofcommunication resources.

Optionally, the adaptively selecting between at least two sidelink (SL)communication resource configurations to be used by the UE for SLtransmissions is based on one or a combination of two or more of:traffic type, packet size, reliability target, latency target.

Optionally, sidelink control information comprises a resource allocationand power level for a sidelink transmission.

According to another aspect of the present disclosure, there is provideda UE configured to perform one of the methods summarized above ordescribed herein.

A computer program product could include a non-transitory computerreadable storage medium storing programming, the programming includinginstructions to perform any one or a combination of methods as disclosedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1A is a block diagram illustrating an example of a two-dimensionalresource configuration for grant-free SL transmission.

FIGS. 1B-1K are block diagrams illustrating other examples oftwo-dimensional resource configurations for grant-free SL transmission.

FIG. 2 is a block diagram illustrating another example of anothertwo-dimensional resource configuration for SL transmission.

FIG. 3A is a block diagram illustrating an example of two different waysof configuring a transmission pattern for a time-domain resourceconfiguration.

FIG. 3B is a block diagram illustrating another example of how atransmission pattern could be configured.

FIG. 4 is a block diagram illustrating an example of a transmissionpattern that is defined within a configured RP.

FIG. 5 is a block diagram illustrating an example of an RRC signaledtransmission pattern for an SL transmission scheme.

FIG. 6A is a flow diagram illustrating an example of a distributedgrant-free transmission mode for SL communications.

FIG. 6B is another signal flow diagram illustrating an example of adistributed grant-free transmission mode for SL communications

FIG. 7 is a block diagram illustrating an example of a semi-persistentscheduling (SPS) signaled transmission pattern for an SL transmissionscheme.

FIG. 8 is a signal flow diagram illustrating an example of SLtransmission mode using SPS.

FIG. 9 is signal flow diagram illustrating an example of an SL scheduledtransmission scheme.

FIG. 10 is a signal flow diagram illustrating an example of a UEcooperation using SL transmission.

FIG. 11A is a plot illustrating an example of a configuration of an SA.

FIG. 11B is another plot illustrating an example of a configuration ofan SA.

FIG. 12 is a block diagram illustrating an example of a group basedconfiguration for distributed grant-free SL transmission in a network.

FIG. 13 is a flow diagram illustrating an example of a method forsidelink communications.

FIG. 14 is a block diagram illustrating an example of atelecommunications network according to one embodiment.

FIG. 15 is a block diagram illustrating an example of a network servingtwo UEs.

FIG. 16 is a flowchart of a method of SL transmission based on decodedSL control information;

FIG. 17 is a flowchart of a method of SL transmission based on SLmeasurement;

FIGS. 18A to 18D are examples of resource patterns

FIG. 19 is a flowchart of a method of SL transmission in which resourcesfor SL transmission are adaptively adjusted based on decoding of SLcontrol channel and/or measurements of SL transmission resources;

FIG. 20 is an example of multiple SL transmission resourceconfigurations that are selected between;

FIG. 21 is a flowchart of a method of SL transmission in which the UEadaptively selects between two SL communication resource configurations.

FIG. 22 shows an example of flexible start time within arepetition/transmission pattern.

FIGS. 23 to 26 show example simulation results.

DETAILED DESCRIPTION

For illustrative purposes, specific example embodiments will beexplained in greater detail below in conjunction with the figures. Itshould be appreciated, however, that the present disclosure providesmany applicable concepts that can be embodied in a wide variety ofspecific contexts. The specific embodiments discussed are merelyillustrative and do not limit the scope of the present disclosure.

A conventional long-term evolution (LTE) SL transmission scheme relieson the concept of a resource pool (RP) defining a pool of communicationresources that are available for SL communication. The SL is used forboth transmit (Tx) and receive (Rx) functions, and a UE may not be ableto both transmit and receive communications at the same time, i.e., itcan either transmit or receive sidelink communications at one time. Thisis because UEs are typically half duplex devices.

The conventional LTE SL transmission scheme includes two transmissionmodes, known as “mode 3” and “mode 4”.

In mode 3, a BS transmits to a UE control information using a “downlinkcontrol information” (DCI), which schedules time-domain andfrequency-domain communication resources (from an RP) for SLtransmission. This scheduling may be performed dynamically orsemi-persistently using a DCI. However, scheduling of the SLtransmission resources by the BS results in latency. Before the UE cantransmit on the SL, it must wait for the DCI from the BS. Furthermore,the dynamic nature of the resource scheduling increases the signalingoverhead associated with an SL transmission.

In mode 4, the UE autonomously selects resources within the RP, whichavoids the latency issue associated with mode 3. However, the RP in mode4 is not designed to prevent two UEs from selecting the same resourcefor SL communication. Since there is no direct control, by the networkor the BS, of the resources used for SL communication within the RP, twoUEs can cause a message collision by independently selecting the sameresource. When this happens, the collision may cause reliability issuesfor the message, which may not be successfully decoded by the intendedreceivers.

Aspects of this disclosure provide a new SL transmission mode forcommunications in a wireless network. In this disclosure, the new SLtransmission mode may be referred to as a “grant-free transmission mode”or as a mode for data transmissions that are performed withoutcommunicating dynamic scheduling.

In conventional UL transmissions, whether they be grant-based or“grant-free,” the BS knows the parameters and resources used for the ULtransmission because those parameters and resources are configured bythe BS. This greatly reduces the complexity of the UL transmission, andparticularly it does not require uplink control signaling to beassociated with the UL transmission to indicate the transmissionresources and parameters used for the UL transmission. In a grant-basedUL transmission, for example, the required transmission parameters aretypically communicated to a UE via a Physical Downlink Control Channel(PDCCH). The base station is aware of the identity of the UE sending theUL transmission using the granted UL resources, because the BSspecifically granted those UL resources to that UE in a scheduling grantsent in PDCCH.

In a conventional UL grant-free transmission from a UE to a BS, forexample, different UEs could send UL transmissions using ULcommunication resources configured semi-statically in UE-specific RRCsignaling, without specifically requesting use of the resources in adynamic manner, and without receiving a dynamic scheduling grant of theresources sent in a DCI by the BS. The grant-free transmission typicallyachieves low latency and reduced scheduling overhead as compared to thegrant-based UL transmission. The BS receiving the grant-free ULtransmission knows the communication parameters of the UL transmissionbecause the BS has previously configured the UE performing thegrant-free UL transmission semi-statically. Although, the BS may nothave complete information about which UE, if any, is sending agrant-free UL transmission at a particular moment of time if multipleUEs are configured to be able to access the same resources, the BS isable to detect the grant-free transmissions and determine the UE basedon the configuration parameters (e.g. using DMRS parameters and time andfrequency resources).

While it is also desirable to achieve the advantages of grant-freetransmission for SL communications between UEs, the nature of SLcommunications creates particular challenges for implementing grant-freetransmissions. In contrast to UL grant-free transmissions where thereceiver is a BS with high awareness, both the transmitter and receiverare UEs in SL grant-free transmissions. Therefore, the receiving UE isnot aware of the transmitting UE's configuration parameters, such aswhich UE is transmitting, the ultimate target of the data (e.g., anotherUE), the time-domain and frequency-domain communication resources usedfor the transmission, and other control information.

The present disclosure presents a new grant-free transmission mode forSL transmission, which includes an SL control channel, also known asscheduling assignment (SA), or sidelink control information (SCI) tomitigate the challenges associated with implementing grant-freetransmissions in SL communications. The SL control channel may includecontrol or configuration information such as information indicatingwhich UE is transmitting, the target UE or BS for the data, thetime-domain and frequency-domain communication resources used for thetransmission, and/or other configuration information. A receiving UE maydecode the SL control channel first to obtain this information beforedecoding the data transmission.

Grant-free transmissions are sometimes called “grant-less”, “schedulefree”, or “schedule-less” transmissions. Grant-free SL transmission canalso be referred to as SL “transmission without grant”, “transmissionwithout dynamic grant”, “transmission without dynamic scheduling”, or“transmission using configured grant”, for example.

In various embodiments, the transmitting UE indicates its specific SLtransmission pattern to a destination UE or multiple destination UEs inthe SL control channel. The SL transmission pattern is configured by theBS, to enable grant-free SL communications. The specific SL transmissionpattern allows a grant-fee SL communication from one UE to avoidcolliding with a grant-free SL communication of another UE.

The term collision as used herein refers to a situation in whichmultiple UEs are transmitting signals using the same communicationresource or overlapping communication resources, such that the multipleUEs' transmission signals may interfere with each other, making it moredifficult for the respective receivers to decode the transmittedsignals. For example, a collision occurs when UEs that are transmittingin the same time-frequency resource in the same time slot.

Collision represents an example of a scenario in which an SLtransmission by a UE might not be received by another UE. Half duplexdevices, as noted above, can either transmit or receive sidelinkcommunications at any time. A half duplex UE cannot receive an SLtransmission while it is also transmitting. SL transmission patternscould also or instead be used to mitigate the problem of missing signalsfrom one or more other UEs due to transmitting at the same time.

An SL transmission pattern represents a sparse set of communicationresources. More specifically, the SL transmission pattern defines howcommunication resources are to be used by UEs for SL transmissions, andcan be designed to enable all UEs in a cooperation group to communicatewith each other even if some transmissions are transmitted in agrant-free manner (i.e., without dynamic scheduling). This could beespecially useful in applications such as V2X and UE cooperation, and/orother applications as well.

In some embodiments, the transmission pattern indicates a number of “on”or usable resources within the time window of the transmission pattern.In a time-frequency based transmission pattern, for example, the UEtransmits using time-frequency communication resources in time slotsthat are designated as “on” time slots by the transmission pattern, andreceives in time slots that are not designated as “on” time slots (orare otherwise designated as “off” time slots) by the transmissionpattern. In this sense, a transmission pattern could be considered aform of “on-off” pattern in some embodiments.

The transmission pattern (or, in some embodiments, the on-off pattern)may define the resources used for a number of transmissions of atransport block (TB). The transmissions may include the initialtransmission and retransmissions of the same TB. The initialtransmission and retransmission of the TB may sometimes also be referredto as repetitions. In some embodiments, each transmission pattern mayrepresent transmissions of one transport block (TB), i.e., a UE shouldstart initial transmission of a TB at the first “on” slot in thetransmission pattern, and continue repetition of the TB on all the “on”slots until the end of the “on” slots defined by the transmissionpattern. In this type of application, a transmission pattern (or on-offpattern) could be considered a repetition pattern. In some embodiments,a UE may also listen to other UE's transmissions in the “off” slotsdefined by the transmission pattern or any slot that is not defined asan “on” slot in the transmission pattern. This can be done by checkingwhether there is an SA transmitted from other UEs, and if an SA isdetected, the UE may further check whether the associated datatransmission is destined to the UE, and if so, the UE may use theinformation from the SA to further decode the data transmission that isdestined to this UE. Alternatively, a UE may listen to other UEs orcheck other UE's SL control information as long as it is nottransmitting in the same slot.

The present disclosure also provides signaling mechanisms for theproposed grant-free SL communications. As described above, SL controlchannels may be used to accommodate SL data transmission. Someembodiments described herein outline signaling mechanisms that could beused to for grant-free SL communications using transmission patterns.

In some embodiments, a UE is configured to use a transmission patterndefining or otherwise indicating communication resources that areallotted or allocated to the UE over a specific time interval for SLcommunications. Other UEs are similarly configured to use respectivetransmission patterns over this time interval. A UE can transmit andreceive SL transmissions within a time interval using thesecommunication resources according to its transmission pattern. Ahalf-duplex UE might still be transmitting at certain times while otherUEs are transmitting, but transmission patterns could be designed toprovide an opportunity for each UE to receive SL transmissions from allother UEs at least once during the time interval if all UEs areconfigured and transmitting during the time interval using theirrespective transmission patterns.

Time is one dimension that may be used in defining communicationresource usage in a transmission pattern. Other dimensions, such asfrequency, code, and/or signature are also contemplated.

Transmission patterns may belong to a transmission pattern set or poolthat is common to a group of UEs. RRC signaling may be used to configurethe transmission pattern for a UE and/or a transmission pattern pool, aswell as the communication resources for SL data and control.Transmission pattern pool may also be signaled by broadcast signaling(e.g. in SIB).

In an embodiment referred to as mode 1, an example of distributedgrant-free communication is provided. In this embodiment, RRC signalingconfigures a transmission pattern for a specific UE.

In an embodiment referred to as mode 2, another example of distributedgrant-free communication is provided. RRC and system information block(SIB) signaling configure or pre-define a transmission pattern pool, anda UE randomly selects a transmission pattern from within thetransmission pattern pool. A common transmission pattern pool can bedefined for RRC_idle and RRC_inactive UEs, for example.

The above embodiments are distinct from conventional SL transmissionmodes. Compared to mode 3, in which the resource is dynamicallyscheduled by a DCI, the resource is semi-statically configured in theabove mode without a dynamic grant. Furthermore, the scheduling in theseembodiments may be accomplished by RRC signaling, rather than DCIsignaling in mode 3. Compared to mode 4, the UE in these embodimentsdoes not perform autonomous resource selection, as the UE transmitsaccording to the configured transmission pattern. In embodiments, theRRC signaling may configure the transmission pattern to mitigatepotential collisions or reduce the impact of the half duplex constraintbetween the SL transmissions of the UE and SL transmissions of otherUEs. Furthermore, in LTE V2X, the UE may be configured with a receive RPsimilar to a transmitter RP, where a UE should listen to all channelswithin the received RP. In grant-free SL transmission modes describedherein, there is no need to configure a transmit and receive RP.

Embodiments disclosed herein also differ from NR's configured grant orgrant-free UL transmission in several aspects. First, some of theembodiments disclosed herein relate to grant-free SL transmissions, andtherefore the resource configuration for these transmissions is fordifferent channels than in UL transmission. For example, in the SL, thePSSCH (physical sidelink shared channel) and PSCCH (physical sidelinkcontrol channel) may be configured, as opposed to the PUSCH (physicaluplink shared channel) in the UL. Second, in UL transmissions, thereceiver (a BS, for example) knows the resource configuration of the UL,as described above. In contrast, in the SL, resource configuration isnot known by the receiver (a UE, for example). Third, in configuredgrant UL transmission, only a repetition number can be configured, not atransmission pattern. In NR's configured grant UL transmission, therepetitions according to the repetition number, if configured, areperformed in the slot immediately following initial transmission. Thisis because NR UL does not have the issue of half duplex constraint asall UEs only transmit in the UL and do not need to listen in the UL.

In distributed grant-free mode for SL transmission as disclosed herein,a UE could use a transmission pattern to transmit and retransmit a datablock with a fixed repetition number according to the transmissionpattern, without any HARQ feedback. In this type of application, atransmission pattern could be considered a repetition pattern.

In further embodiments, a transmission pattern pool can be applied to UEgroups for UE cooperation. A UE may select a transmission pattern fromthe transmission pattern pool according to its UE index or the UE mayrandomly select a transmission pattern from the transmission patternpool, for example.

In some embodiments, the SL transmission may use cyclic-prefix (CP)orthogonal frequency division multiplex (OFDM), similar to the waveformused for LTE downlink transmission. In some embodiments, the sidelinktransmission may use single carrier frequency division multiple access(SC-FDMA), similar to the waveform used for LTE uplink transmission. Insome embodiments, the sidelink transmissions may use non-orthogonalmultiple access (NOMA), such as: sparse code multiple access (SCMA),interleave-grid multiple access (IGMA), multi-user shared access (MUSA),low code rate spreading, frequency domain spreading, non-orthogonalcoded multiple access (NCMA), pattern division multiple access (PDMA),resource spread multiple access (RSMA), low density spreading withsignature vector extension (LDS-SVE), low code rate and signature basedshared access (LSSA), non-orthogonal coded access (NOCA), interleavedivision multiple access (IDMA), repetition division multiple access(RDMA), or group orthogonal coded access (GOCA).

Illustrative embodiments will now be described in more detail below.

FIG. 1A is a block diagram illustrating an example of a two-dimensionalresource configuration for grant-free SL transmission. FIG. 1illustrates a resource grid 100, which includes frequency-domainresources F0, F1, F2 and F3, and time-domain resources T0, T1, T2, T3and T4. Each combination of frequency-domain resource and time-domainresource forms a communication resource for SL transmission. FIG. 1Aalso illustrates a transmission pattern for a UE1. Resource grid 100indicates a time-frequency communication resource for two transmissionsby UE1, as well as a redundancy version (RV) (RV0 or RV3) in a label oneach communication resource.

In FIG. 1A, UE1 is configured with a transmission pattern, whichexplicitly defines the transmission repetition number as well as thecommunication resources for each repetition. Each repetition may also beassociated with an RV, which can be predefined or preconfigured (e.g.configured using a UE specific RV sequence indicating the associated RVfor each repetition). A single UE index is used to indicate bothtime-domain and frequency-domain resources in FIG. 1A. In general, a UEindex corresponds to a specific UE or a UE group. The communicationresources assigned to UE1 form the transmission pattern for UE1.

The resource grid 100 has a frequency-domain length of 4 and atime-domain length of 5. In the time-domain, T0 to T4 could be slots,mini-slots, symbols, or any other quantization or unit of time. In thefrequency-domain, F0 to F3 could be frequency sub-channels, combinationsof sub-channels, resource blocks, resource block groups (RBGs),bandwidth parts (BWPs), subcarriers, a number of subcarriers, carriersor any other quantization or unit of frequency. Different frequencydomain sub-channels are just an example. Sub-channels can instead beassociated with different layers of non-orthogonal multiple access(NOMA), different pilot resources, and/or other resources. Althoughshown as time-domain resources and frequency-domain resources in FIG.1A, in general the transmission pattern could also or instead includecode-domain resources (such as sparse code multiple access),space-domain resources, and/or different demodulation reference signals(DMRS). Moreover, the transmission patterns are not limited totwo-dimensions, and therefore could include a number of dimensionsgreater or less than two.

In some embodiments, frequency-domain resources, pilots and layer indexmay be associated with time-domain signatures. For example, as analternative to using a UE index, the resource grid 100 could indicateonly the time-domain signature or time-domain transmission pattern, andother dimensions (e.g. the frequency-domain dimension) may be derivedfrom it.

FIG. 1B is another block diagram illustrating an example of atwo-dimensional resource configuration for grant-free SL transmission.FIG. 1B illustrates a resource grid 102. Resource grid 102 includes thesame frequency-domain resources F0, F1, F2 and F3, and time-domainresources T0, T1, T2, T3 and T4 as resource grid 100 in FIG. 1A. FIG. 1Balso illustrates a transmission pattern for UE2.

Resource grid 102 indicates time-frequency communication resources fortwo transmissions by UE2, as well as a redundancy version (RV0 or RV3)in a label on each communication resource. These time-frequencycommunication resources define the transmission pattern for UE2. Thetime-frequency communication resources indicated in resource grid 102for UE2 are different from the time-frequency communication resourcesindicated in resource grid 100 for UE1.

FIGS. 1C, 1D, 1E, 1F, 1G, 1H, 1I and 1J are further block diagramsillustrating other examples of two-dimensional resource configurationsfor grant-free SL transmission. FIGS. 1C, 1D, 1E, 1F, 1G, 1H, 1I and 1Jillustrate resource grids 104, 106, 108, 110, 112, 114, 116 and 118,respectively, each resource grid including the same frequency-domainresources F0, F1, F2 and F3, and time-domain resources T0, T1, T2, T3and T4 as resource grid 100 in FIG. 1A. Resource grids 104, 106, 108,110, 112, 114, 116 and 118 each indicate communication resourcesdefining the transmission patterns for UE3, UE4, UE5, UE6, UE7, UE8, UE9and UE10, respectively, as well as a redundancy version (RV0 or RV3) ina label on each communication resource. Each communication resourceindicated by resource grids 100, 102, 104, 106, 108, 110, 112, 114, 116and 118 are unique.

FIG. 1K is yet another block diagram illustrating a two-dimensionalresource configuration for grant-free SL transmission. FIG. 1Killustrates resource grid 120, which also includes the samefrequency-domain resources F0, F1, F2 and F3, and time-domain resourcesT0, T1, T2, T3 and T4 as resource grid 100 in FIG. 1A. Resource grid 120is a superposition of resource grids 100, 102, 104, 106, 108, 110, 112,114, 116 and 118. Therefore, resource grid 120 may be considered toindicate a transmission pattern pool, which includes the transmissionpatterns for UE1-UE10.

The communication resources illustrated in FIG. 1K are used for SLtransmission by respective UEs, according to their transmissionpatterns. In general, each communication resource represents a potentialtransmission of a transport block (TB). The same TB is used in eachtransmission by a UE over the length of a transmission pattern. Theremay be control information (SA) associated with the TB to be transmittedon separate resources in PSCCH channel.

In FIG. 1K, according to their respective transmission patterns, each UEtransmits a TB twice over the length of the configured transmissionpattern, therefore the repetition number of each transmission pattern is2. As explained below, this allows each UE receive at least onetransmission of the TB by the other UEs.

UE1 cannot receive in T0 and T1 because of the half duplex constraint.As such, UE1 cannot receive the first transmission of UE2, UE3 and UE4.However, by virtue of the configuration of the transmission pattern poolor UE specific transmission pattern, UE1 is able to receive the secondtransmissions of UE2, UE3 and UE4 in at least one time slot over thelength of the transmission pattern, which is five time slots in thisexample.

Regarding reception, UEs could resolve transmissions from differenttransmitting UEs in any of various ways. In the example shown in FIG.1K, UE5 to UE10 could differentiate the transmissions received from UE1to UE4 using the frequency-domain dimension. Another example is that UE1to UE4 may have overlaps in time and frequency domain resources fortheir first transmission, but they may use different codebook/spreadingcodes or layers to resolve the collision using orthogonal codes ornon-orthogonal multiple access (NOMA) transmission schemes.

In general, the repetitions of each UE transmission over the length of atransmission pattern transmit the same TB. However, the RVs associatedwith the repetitions may be configured differently. In the example shownin FIG. 1K, different RV sequences are used in each repetition. Thus,repetitions of a TB might not necessarily be exactly the same.Repetitions could use different coding parameters such as different RVsequences, for example, to increase the likelihood that a subsequentrepetition can be correctly decoded by a receiving UE after failure of aprevious transmission of the same data block or transport block. Eachrepetition may also be associated with a RV that can be the same ordifferent for different repetitions of the TB, which can be predefinedor preconfigured (e.g. configured using a UE specific RV sequenceindicating the associated RV to each repetition)

At a receiving UE, each transmission from a transmitting UE may beindependently decoded. Alternatively, transmissions from multiple UEs inthe case of UE cooperation during the multicast phase and thecooperation phases may be jointly decoded by the receiving UE.

In some embodiments, low density spreading (LDS) may be applied in thetime-domain to transmissions. More generally, any other type of symbollevel or bit level spreading used in multiple access scheme can beapplied to time domain defined by the transmission pattern instead offrequency domain for such transmissions. For example, the transmissionsymbol may be multiplied by a spreading sequence and the output symbolis spread at different time slot of the transmission pattern.

In some embodiments, the transmission resources in the “on” slot of thetransmission pattern may be combined together to transmit a biggertransport block.

In some embodiments, each transmission resource in the “on” slot of thetransmission pattern may be used to transmit independent packets. Itshould be understood that FIGS. 1A-1K provide possible examples of atransmission pattern configuration and transmission pattern pool. Othertransmission pattern pools using different numbers of time-domainresources, frequency-domain resources, and/or other communicationresources are possible. In addition, other configurations oftransmission patterns included in the transmission pattern pool arepossible. For example, for a two-dimensional transmission pattern poolwith a repetition number (K) of 2, a length of time-domain resources of(M), and a length of frequency-domain resources of (N=M+1), the numberof transmission patterns the transmission pattern pool can support andallow for each UE to receive a transmission by each other UE in at leastone transmission/reception slot could be defined as:

$\begin{matrix}{{{number}\mspace{14mu} {of}\mspace{14mu} {repetition}\mspace{14mu} {patterns}} = {\frac{M*N}{K}.}} & (1)\end{matrix}$

FIG. 2 is a block diagram illustrating another example of anothertwo-dimensional resource configuration for SL transmission. FIG. 2illustrates resource grid 200. FIG. 2 also illustrates a UE index(identified as UE1, UE2 . . . or UE 10) and an RV sequence (which is {00 0 0} indicating that every transmission uses RV0) assigned to eachcommunication resource.

In FIG. 2, as in FIG. 1K, each UE index (UE1 to UE10) is configured witha transmission pattern, which defines the transmission repetition numberas well at the communication resources for the repetitions. A single UEindex is used to indicate both communication resource domains (time andfrequency domain or time and code domain, for example). Thecommunication resources assigned to UE1 are part of the transmissionpattern for UE1. Similarly, the communication resources assigned to UE2to UE10 are part of the transmission patterns for these UE indexes. Thecollection of these transmission patterns forms a transmission patternpool.

A UE may be configured with a transmission pattern pool and randomlyselect a transmission pattern from the transmission pattern pool. In oneembodiment of configuring the transmission pattern pool, a repetitionnumber (K) and a length of the transmission pattern are indicated. Inone embodiment, all transmission patterns that satisfy the K and lengthparameters and a given range and partition of time granularity (e.g.slot T0 to T4 in FIG. 1K) and frequency sub-channels (e.g. F0-F3 in FIG.1K) that are included in the transmission pattern pool are considered tobe the candidate transmission patterns among the pattern pool. The rangeand partition the frequency sub-channels (F0-F3 in FIG. 1K) may also beindicated for the transmission pattern pool. In another embodiment, notevery possible transmission pattern that satisfies the K and lengthparameters are necessarily included in the transmission pattern pool.Only a subset of all of the possible transmission patterns could beselected for the pool. An example of such subset of possibletransmission patterns among the pattern pool are the transmissionpatterns corresponding to UE1 to UE10 as indicated in FIG. 1K. A UE mayalso be configured with starting time location of the transmissionpattern for the transmission pattern pool configuration.

In order for a UE to transmit without dynamic grant on the SL accordingto a transmission pattern, the transmission pattern or transmissionpattern pool must somehow be determined by the UE, and could be signaledto the UE. The signaling of transmission patterns and/or transmissionpattern pools could be done through, for example, system informationblocks (SIB), cell specific RRC signaling, UE specific RRC signalingand/or DCI signaling.

The different dimensions of the resource configuration could beconfigured separately using UE specific RRC signaling. Alternatively, acombination of two or more of time-domain, frequency-domain,code-domain, DMRS and other resources could be configured together usinga single UE index. The signaling of the UE index can be UE specific RRCsignaling or any of the signaling methods described above. The mappingbetween the UE index and communication resources in a transmissionpattern may be performed by a UE, or may be predefined and/or signaledto the UE by RRC signaling. The mapping may be in a form of a mappingtable or a rule or equation that defines the resources in differentdimensions for a given UE index. The mapping table or rule, ifpredefined, should be such that each UE is able to receive at least onetransmission from each of the other UEs. As in the example shown inFIGS. 1A, 1B, and 1K, the transmission of two different UEs (e.g. UE1and UE2) in the same slot may be mapped to different frequencysubchannels. In addition, if two UEs (or UE indices) have a firsttransmission of a TB at the same time slot, then their secondtransmission should be mapped to a different time slot to overcome thehalf duplex constraint. For example, for K=2, a one to one mapping of M(M=4 in FIG. 1A-1K) frequency-domain resources can be created with anM+1 length time-domain pattern, to support M*(M+1)/2 time-frequencychannels to be allocated to M*(M+1)/2 different UEs.

In some embodiments, a transmission pattern can be defined on resourcesthat are included in a configured RP, or without explicitly configuringa RP.

FIG. 3A is a block diagram illustrating an example of two different waysof configuring a transmission pattern for a time-domain resourceconfiguration. FIG. 3A includes transmission patterns 300, 302, whichinclude “off” slots (one of which is labeled as 304) in which a UE doesnot transmit, and “on” slots (one of which is labeled as 306) in which aUE may perform SL transmissions. SL transmissions may include, forexample, V2X transmissions. In general, slots 304 and slots 306 definethe transmission patterns. Although referred to primarily as slots, eachslot 404, 406 could be, for example, a subframe, a mini-slot, an OFDMsymbol, a number of OFDM symbols or any other time unit.

The transmission patterns 300, 302 of FIG. 3A also include an offset,which indicates the starting location of the transmission patterns, andcould be a slot index or identifier or an offset from a particular slotor the start of a frame for example. The transmission pattern 302 alsoincludes a periodicity, which defines a time gap between startinglocations of two adjacent transmission patterns where the transmissionpatterns may periodically occur over time.

Each transmission pattern may be represented using a bitmap, as shown.In the bitmap {00101011} in FIG. 3, a “1” represents a time unit (e.g. aslot 306) that is available for SL transmission and a “0” represents atime unit (e.g. a slot 304) in which an SL transmission is not performedby a UE that is using the patterns 400, 402. The bitmap may repeatitself without a gap between adjacent repetitions as shown at 300, orwith a gap as shown at 302.

The number of slots 306 within one transmission pattern, four in theexamples shown in FIG. 3A, represents the repetitions number (K) for arepetition pattern, or more generally the communication resources thatmay be used for SL transmissions. As described earlier, the transmissionpattern may define the resources used for a number of transmissions of aTB. The transmissions may include the initial transmission andretransmissions of the same TB. The initial transmission andretransmission of the TB may sometimes also be referred to asrepetitions. In some embodiments, each transmission pattern mayrepresent transmissions of one transport block (TB), i.e., a UE shouldstart initial transmission of a TB at the first “on” slot 406 in thetransmission pattern, and continue repetition of the TB on all the “on”slots 406 using an RV corresponding to the configured or predefined RVsequence until the end of the time defined by the transmission pattern.Thus, in some embodiments, the transmission pattern indicates therepetition number (K). In some embodiments, a UE may also listen toother UE's transmissions in the “off” slots defined by the transmissionpattern or any slot that is not defined as an “on” slot in thetransmission pattern. This can be done by checking whether there is anSA transmitted from other UEs, and if an SA is detected, the UE mayfurther check whether the associated data transmission is destined tothe UE, and if so, the UE may use the information from the SA to furtherdecode the data transmission that is destined to this UE. Alternatively,a UE may listen to other UEs or check other UE's SL control informationas long as it is not transmitting in the same slot.

Control signaling to configure transmission patterns could include abitmap as shown in FIG. 3A. Signaling could also indicate theoffset/starting point of the transmission pattern.

As illustrated by the transmission pattern 300, the offset or startingtime location defines a starting time location of one transmissionpattern, and the transmission pattern could repeat among all availableslots, such as all slots in a larger frame. For example, thetransmission pattern could repeat within a larger time frame, e.g. 10240subframes, excluding DL only or DL dominant slots. The larger time framecan be the length defined by the maximum allowable system frame number(SFN). For example, in LTE or NR, the maximum SFN is 1024 and eachsystem frame consist of 10 subframes, thus the larger time frame isequal to 10240 subframe or 10240 ms with each subframe equal to 1 ms. Insome embodiments, at the end of the larger time frame (10240 subframesfor example), there might not be enough additional subframes for anothercomplete repetition of the transmission pattern. Instead of having atransmission pattern “split” across a time frame boundary, with apartial transmission pattern after 10240 subframes and continuing in thenext 10240 subframes, the transmission patterns could have the samerelative location within each set of 10240 subframes. In other words,the transmission pattern may be defined within a larger time frame,where the starting location and periodicity are defined as the locationwithin the larger time frame, and different larger time frame have thesame relative location of transmission patterns.

As shown at 302, the periodicity could be defined the time domain gapbetween starting locations of two adjacent transmission patterns, suchas when there are otherwise allocated resources or some other gapbetween two adjacent transmission patterns. The resources for thetransmission pattern may occur periodically, and that is defined by theoffset and periodicity in some embodiments, where offset indicates thestarting time location of a transmission pattern and the transmissionpattern appears periodically with the gap between two transmissionpatterns as periodicity. In some cases, a BS may signal the periodicityusing RRC signaling.

In some embodiments, instead of indicating the starting time location ofthe transmission pattern, a BS may instead indicate the starting timelocation of the initial transmission of the TB. An example of suchindication of the starting time location is shown in FIG. 3B, which is ablock diagram illustrating another example of how a transmission pattern310 could be configured.

In other embodiments, the bitmap that indicates the transmission patternalways start with ‘1’, in which case, the starting time location(offset) of the transmission pattern is the same as the starting timelocation of the initial transmission of a TB. A transmission pattern asshown at 310 could then be configured with a bitmap {101011}, a startinglocation of the initial transmission, and a periodicity. Anotherpossible configuration, if transmission patterns repeat without a gap asin FIG. 3A, could use a bitmap {10101100} and a starting location of theinitial transmission, with the trailing zeros at the end of the bitmapinstead of leading zeros for non-transmission slots.

FIG. 4 is a block diagram illustrating an example of a transmissionpattern that is defined within a configured RP. This is an example ofincluding a transmission pattern in an RP, or transmission patternconfiguration on top of (or overlaid on) RP configuration. FIG. 4includes RPs 400, 402. The RPs 400, 402 include slots, which as notedabove with reference to FIG. 3A could be other types of time units. FIG.4 also illustrates an RP period and a starting slot.

Two types of slots are shown in the RP 400. Slots 404 are available forSL transmissions, and slots 406 are not available for SL transmissions.The configuration of the RP can be cell specific or UE specific, e.g. inUE specific or cell specific RRC signaling or system information.

The RP 402 is overlaid with a transmission pattern. Slots 408 in the RP402 represent particular ones of the available slots 304 that aretransmission slots or “on” slots in a transmission pattern configurationfor a particular UE. In other words, slots 408 may correspond totransmission slots included in the transmission pattern for a UE. OtherSL-available slots in 402 do not correspond to transmission slots in thetransmission pattern, and therefore a UE that is using the exampletransmission pattern shown in FIG. 4 could use these slots to listen fortransmissions from other UEs.

The RP period is the length of time over which the RPs 400, 402 repeat.In some embodiments, the RP period is 10240 ms, corresponding to 1024frames defined using system frame number (SFN), where each frame is 10ms and contains 10 subframes of lms each.

The RPs 400, 402 may be represented using a resource bitmap{00101011},where a “1” represents a time unit (e.g. a slot) that is available forSL transmission and a “0” represents a time unit that is not available.The time unit can be a slot, a subframe, a mini-slot, an OFDM symbol, anumber of OFDM symbols or any other time unit. The resource bitmap mayrepeat within the RP period as shown in FIG. 4.

A starting time unit (e.g. slot) for the transmission pattern may alsobe indicated, as shown by way of example in RP 402. In this example, therepetition number, which is the number of repetitions (including initialtransmission) or transmissions to be performed by the UE for a TB insome embodiments, could be explicitly signaled as a value K=2 orimplicitly indicated through the “on” slots in the transmission pattern.Further, the transmission pattern that is overlaid on RP 402 may also bepresented in a time-domain transmission pattern bitmap beginning at thestarting slot, and in this example the bitmap is {01010000}. Thestarting slot, or in general, the starting time location, may beindicated as an offset, which defines the actual time location of thebeginning of the transmission pattern. The offset can indicate anabsolute time location or a time location with respect to SFN=0, i.e.the location within the duration defined by the maximum system framenumber. The offset may be defined as a slot number, a symbol number orany other granularity of time unit. For example, with a maximum SFN of1024 as in LTE or NR, the offset may define a slot number within 1024frames or 10240 subframes. In a time-domain transmission pattern bitmap,a “1” corresponds to an “on” transmission slot (or in general atransmission time unit) in the transmission pattern for a specific UE,and a “0” corresponds to an “off”, non-transmission slot in thetransmission pattern for a specific UE. As shown in FIG. 4, thetransmission pattern bitmap is defined only on the available slots 404within the RP 400. The length of the transmission pattern is the timedomain duration of the pattern. In the example where the time domaintransmission bitmap is {01010000}, the length of the pattern is 8 timeunits. The time-domain transmission pattern bitmap, like the RP bitmap,may also repeat within the RP period. In some embodiments, a UE may alsolisten to other UE's transmissions in the “off” slots defined by thetransmission pattern or any slot that is not defined as an “on” slot inthe transmission pattern. Alternatively, a UE may listen to other UEs orcheck other UE's SL control information as long as it is nottransmitting in the same slot. In some embodiments, a UE only listens toother UE's transmission within the slot defined in RP as long as it isnot transmitting at the same time.

In some embodiments, the time domain resource configuration may defineor directly indicate the time location of an initial transmission of aTB and/or a time gap between the initial transmission of the TB and arepetition of the TB. In some embodiments, the time domainconfigurations could include time domain resource configuration ofphysical sidelink shared channel (PSSCH) and/or physical sidelinkcontrol channel (PSCCH), frequency domain resource configuration ofPSSCH and PSCCH, the transmission pattern, repetition related parameters(e.g. repetition number K, length of the transmission pattern, RVsequence for repetition), code domain resource configuration, waveformconfiguration, resource configuration for DMRS etc. The transmissionpattern can be part of time-domain and frequency domain resourceconfiguration. Each signaling term may be optional. The time-domainresource configuration may also include mini-slot related information,such as the starting symbol and length, in terms of number of symbols ofone transmission, and PSSCH/DMRS mapping type.

The time domain resource configuration may include optionally an RPperiod, optionally an offset (also referred to as starting slot),transmission pattern bitmap, repetition number (K), RV sequence forrepetition, and optionally length of the transmission pattern. If an RPis already configured, the transmission pattern bitmap can be defined ontop of (or overlaid on) RP configuration, as shown in FIG. 4. Theconfiguration can also be done without an RP configuration, as shown inFIGS. 3A and 3B. The meaning of a repetition bitmap with and without aRP configuration should be clear from FIG. 4 (with RP configuration) andFIGS. 3A-3B (without RP configuration), respectively.

The frequency domain resource configuration may include, for example,the active Bandwidth part (BWP) used for SL transmission andsubchannels/Resource block group (RBG) of the BWP. There may be twodifferent types used to indicate the frequency domain subchannels. Type0 may indicate continuous RBs for the resource allocation, whichindicates the starting RB (or RBG) location and number of resourceblocks (RBs) or number of RBGs. In some embodiment, the starting RBindicated is the starting virtual RB (VRB), for which the actualphysical location of RB, known as physical RB (PRB) is derived from VRBand hopping configuration parameters if frequency hopping is configured.Type 1 may indicate which RBGs or subchannels among all the availableRBGs or subchannels are active. The number of RBs in each RBG orfrequency subchannel and starting RBs of the first RBG/frequencysubchannel may be also configured by RRC or system information. Type 1can be indicated using a RBG or subchannel bitmap, where each bit of theRBG or frequency subchannel bitmap indicates whether the correspondingRBG or frequency subchannel is used or not. There may be an additionalflag to indicate whether the frequency resource indication is using type0, type 1 or is dynamically switching between type 0 and type 1.

In some embodiments, the frequency domain configuration may firstindicate the starting RB of the first frequency sub-channel(RB_{start}), number of RBs per frequency subchannel(N_{RB_in_subchannel}), and the total number of frequency sub-channels(n_{subchannel}) available for the SL transmission. The above parameterscan be used to determine the range and partition of frequencysubchannels. For example, in a resource grid as shown in in FIG. 1A, theabove parameters (starting RB of F0, number of frequency sub-channels is4 and the number of RBs per sub-channel is the number of RBs in F0) candefine the frequency location and size for F0 to F4. The aboveparameters can be UE specifically indicated (e.g. in RRC) or can bebroadcast in system information for multiple UEs. The frequency domainconfiguration may then indicate the index of the frequency subchannel mto be used for the transmission. UE may then determine its frequencyallocation corresponds to the RB that starts at RB indexRB_{start}+m*N_{RB_in_subchannel} and with n_{subchannel} number ofcontinuous RBs to be use. In the case, a transmission pattern bitmap isdetermined in time domain and different subchannels may be used infrequency domain for different repetitions of the TB, the frequencydomain configuration may further indicates the frequency index for eachtransmission/repetition of the TB. For example, in case of the exampleshown in FIG. 1A, F0 to F4 may corresponds index m as 0, 1, 2, 3,respectively, and the frequency domain resource configuration mayindicate a frequency channel index sequence corresponding to eachtransmission of the TB, which is {0, 2}, corresponding to F0 and F2 forfirst and second transmission of the TB.

The time and frequency domain resource configuration for the SL controlchannel PSCCH (or SA) may share the same above configuration for SL datachannel or have their own separate configuration. In some embodiments,the resource configuration for an SA shares the parameters above withthe data channel configuration, but has the following additionalconfigurations, which may include starting symbol and length of a SA interms of number of symbols, a time gap between SA and the correspondingdata transmissions if SA and data transmission are in different slots(see, for example, FIGS. 11A and 11B described below), and thefrequency-domain resource configuration of SA. For example, thefrequency domain resource configuration of SA may include a startingfrequency domain communication resource and a size of a SA in thefrequency domain (e.g. in terms of resource blocks, the starting RB andthe size of SA in number of RBs). There may be a parameter used toindicate whether the SA and data is in frequency division duplex (FDD)mode or time division duplex (TDD) mode and/or whether the SA and dataare in different slots.

In some embodiments, SA and the corresponding SL data transmission maybe FDDed as in FIGS. 11A and 11B. The starting RB for the SA may sharethe starting RB configuration for the SL data, which can be derived forexample as RB_{start}+m*N_{RB_in_subchannel}. The number of RBs for SAs_{RB_in_SA} may be UE specifically configured (e.g. in RRC), cellspecifically configured (e.g. in system information block) or predefined(e.g. a fixed number 2). The resources for the SL data transmission mayneed to exclude the resources used for SA transmission. For example, theSL data transmission in the case of FDD may be starting atRB_{start}+m*N_{RB_in_subchannel}+s_{RB_in_SA} instead ofRB_{start}+m*N_{RB_in_subchannel}. In some embodiment, when UE listen totransmission from other UEs, UE may assume SA may be potentiallytransmitted by other UEs in the same frequency location at eachfrequency sub-channel.

Although some embodiments described herein relate to time-domain andfrequency domain resource configuration, in general communicationresources could be configured in other domains or with other parameters.The following is a non-limiting list of examples of parameters that maybe signaled in resources configured in other communication resourcedomains.

Code domain

-   -   Layer index, Signature index or codebook index indicating which        layers/signatures/codebooks to be used for orthogonal or        non-orthogonal multiple access

Waveform

-   -   Discrete Fourier transform spread orthogonal frequency division        multiplexing (DFT-S-OFDMA);    -   Cyclic prefix OFDMA (CP-OFDMA) or whether transformed coding is        enabled.

Frequency hopping for PSSCH

-   -   Frequency hopping offset (if frequency hopping is enabled).        Frequency hopping offset may indicate the number of RBs or RBGs        that are hopped from one slot to its adjacent slot and/or from        the first half of a slot to the second half of a slot within the        available bandwidth in a BWP.

Reference signal (RS)

-   -   PSSCH/DMRS mapping type. Type A may indicate the DMRS location        is at fixed symbols among the slot. Type B may indicate the DMRS        symbol location depends on the starting and ending symbol        configuration of the data resource.    -   DMRS location and symbols. Which may indicate how many DMRS        symbols are used and location of DMRS symbols.    -   DMRS sequence initialization;    -   Antenna port;    -   number of layers;

Note that different transmissions of the TB defined in a transmissionpattern may share the same parameters configured in domains other thantime domain or different transmissions of the TB may use differentresources for the other domains as well. In the first scenario, only oneset of resources in the respective domains would be configured. In thelatter scenario, a corresponding transmission pattern in each respectivedomain may be configured for each transmission of the TB. For example,to signal a transmission pattern in FIG. 1A to FIG. 1K, the BS maysignal to the UE the frequency location of the transmission pattern foreach UE at each transmission of a TB. For example, a BS may signal thepartition (e.g. available bandwidth and number of RBs for each RBG orfrequency subchannels) of the frequency sub-channels (F0-F3)) and indexof the frequency sub channels used for each transmission/repetition ofthe TB (only 2 repetitions in FIG. 1A to FIG. 1K). In some otherembodiments, the same set of parameters may be used for all thetransmissions of the TB in other domains. For example, the set offrequency domain location configuration parameters may be used todetermine all the frequency domain locations of the transmissions of thesame TB (with the possible exception of frequency hopping, which coulddefine a frequency location change at different time locations).

FIG. 5 is a block diagram illustrating an example of an RRC signaledtransmission pattern for an SL transmission scheme. FIG. 5 includes anSL channel 500, RRC signaling 502, and communication resources 506, 508,510.

In FIG. 5, the RRC signaling 502 signals a transmission pattern and/orlocations of the communication resources 506, 508, 510. Thecommunication resources 506, 508, 510 may include the resources used forSL control channel (a PSCCH or an SA) and the resources used for SL datatransmission (PSSCH).

In embodiments described herein, a BS may broadcast system informationto all the UEs in a cell. The system information (e.g. SIB) mayoptionally contain some parameters of the resource configuration for SLtransmission that is common for all the UEs in the cell. A UE may detectthe corresponding SIB to obtain the common resource configurationparameters before the initial access process or before SL transmissiontakes place. Such configuration by broadcast signaling is not shown inthe flow diagrams below. In addition, all the configuration described inthis disclosure for RRC signaling may be instead or in addition to beconfigured in a medium access control (MAC) channel element (CE).

FIG. 6A is a flow diagram illustrating an example of a distributedgrant-free transmission mode for SL communications. The embodiment shownin FIG. 6A involves RRC signaling, as generally shown in FIG. 5.

FIG. 6A illustrates a BS or network 600, and three UEs (UE1, UE2 andUE3). The BS or network 600 may be any network entity capable ofresource configuration for SL communication, such as a transmit andreceive point. The BS or network 600 is in communication with UE1, andcould also be in communication with UE2 and UE3, UE2 and UE3 could be inrange of BS or network 600 or out of range of BS or network 600. UE1,UE2, UE3 in FIG. 6A each represent one or more UEs. Any of the UEs UE1,UE2, UE3 could be a group of UEs. For example, if UE2 representsmultiple UEs, then the transmission step in 612 is a multicasttransmission with multiple destination UEs instead of a unicasttransmission with one destination UE. In addition, UE2 and UE3 could bethe same or different UE(s).

FIG. 6A includes several transmissions, including an optional request602 for SL transmission resource configuration, an RRC configuration 604of resources used for transmissions, transmission 610 of an SA of TB1,transmission 612 of SL data of TB1, transmission 614 of an SA of TB2,and transmission 616 of SL data of TB2.

The optional transmission at 602 is indicated using a dashed arrow inFIG. 6A. UE1 does not always request SL resources at 602 every time ithas data to transmit. There are also various sources of data to betransmitted by UE1, and therefore “data to transmit” blocks 606, 626 arealso shown in dashed lines in FIG. 6A. For example, data fortransmission could be, but need not always be, received by UE1 from theBS or network 600. Data for transmission could arrive at UE1 or begenerated internally by UE1.

FIG. 6A illustrates several operations, including SA decoding operations618 and 622, as well as SL data decoding operations 620 and 624.

In FIG. 6A, an initial request for SL resources may be transmitted fromUE1 to the BS or network 600 using request 602. This request may be fornew SL resources, or for an update to previously configured SLresources. The request 602 can be part of the initial access process forUE1.

Transmission 604 from the BS or network 600 to UE1, whether in responseto a request at 602 or otherwise, could include any of the examples ofresource configuration signaling that have been described herein. TheRRC signaling at 604 could include transmission pattern parameters suchas a transmission pattern bitmap and offset or starting time location,and optionally periodicity of the transmission pattern. It may alsoinclude resource configuration in frequency domain and other domains insome embodiments. The transmission pattern may also define the timelocation of performing initial transmission and repetitions of a TB.Optionally, a transmission pattern may also be included in theconfiguration of SL control resources. This control transmission patternmay be the same as or different from the transmission pattern configuredfor SL data communication resources. After receiving the RRCconfiguration at 604, UE1 has obtained all the resource configurationinformation that it needs to start SL transmissions, without receiving adynamic grant sent in DCI by the BS or network 600 before each SLtransmission. In some embodiments, RRC configuration in 628 might notindicate the configuration of SL control resources or the SL controlresource might not be implicit. SL control resources may also be derivedfrom SL data resources. For example, if the SA resource is FDDed withthe SL data resource as in FIG. 11A and FIG. 11B and the number of RBsfor the SA resource is predefined, then the SA resource may be derivedfrom the configuration of the SL data transmission resources.

As an example of RRC configuration signaling in 604, if a UE is to beconfigured with a transmission pattern shown in FIG. 1B for UE2. The RRCconfiguration may include the time domain transmission pattern bit map{1 0 1 0 0}, optionally the length of the transmission pattern, which is5 slots, the repetition number K, which is 2, a RV sequence associatewith repetitions of the TB, which is {0 3 0 3} or {0 3} indicating thefirst transmission use RV0 and second transmission use RV3, a startingtime location of the transmission pattern or initial transmission, whichis the starting time location of T0, a periodicity of the transmissionpattern. The RRC configuration may further include the starting RB ofthe first frequency subchannel, which is the starting RB of F0, thenumber of frequency subchannels, which is 4, the number of RBs for eachfrequency subchannel, which is the frequency size or number of RBs inF0, F1, F2 or F3. The above parameters for defining the range andpartition of frequency subchannels may be instead configured inbroadcasting signaling (e.g. in SIB). The RRC signaling then may furtherindicate frequency index of each transmission, which is {1, 3},indicating F1 and F3 frequency subchannels used for first and secondtransmission of the TB.

In transmission 610 from UE1 to UE2, after UE1 has data (TB1) totransmit to UE2 at 606, an SA of a TB1 is transmitted using the RRCconfigured SL control resources. The SA indicates the resources andparameters used for data transmission. If a transmission pattern isconfigured for the SL control resources, then the SA of TB1 istransmitted at 610 according to this transmission pattern. UE1 shouldindicate the transmission parameters and resources used for datatransmission in step 612 in the SA at 610, for which the transmissionparameters and resources used for SL data transmission in step 612should be chosen according to the data communication resourcesconfigured in RRC configuration in 604. The SA of TB1 may indicate thetransmission pattern for UE1, which is determined according to thetransmission pattern in the configuration of SL data communicationresources for UE1. The SA of TB1 may include other parameters for the SLtransmission in step 612, which may also be derived from theconfiguration of SL data communication resources for UE1. For example, atime of the initial transmission and the next retransmission in arepetition pattern for SL data transmissions of TB1 could be specified,and then the SL transmissions are performed using the transmissionpattern for UE1 defined by the RRC configured SL data communicationresources. In another example, the SA may include a time gap between thetime location of the SA transmission and the time location of thecorresponding transmission of the TB or the initial transmission of theTB, or the start of the transmission pattern. If the SA is associatedwith one transmission of the TB, the SA may also indicate whichtransmission of the TB it is associated with, and the RV associated withthat transmission. Examples of transmissions according to transmissionpatterns are described above with reference to FIGS. 1A to 4. The SA mayalso include the transmitting UE ID and destination UE ID.

At 618, the SA of TB1 is decoded by UE2, so that UE2 can determine whereto find the information with regards to the resources and parametersused for the data transmission at 612, and the SL data of TB1 is thendecoded at 620 based on the decoded SA.

FIG. 6 also represents at 626 that UE1 has data (TB2) to send to UE3.The transmission 614 from UE1 to UE3, which could be performed before SAand/or data decoding at 618, 620 is complete, illustrates transmissionof an SA associated with TB2, performed using the RRC configured SLcontrol resources after UE1 has data to transmit to UE3. This is similarto transmission 610 to UE2. Here TB2 may differ from TB1, and istransmitted in a different period of the transmission pattern that isdefined for UE1 by the RRC configured SL data communication resources.

In transmission 616 from UE1 to UE3, an SL data transmission of TB2 isperformed using the transmission pattern for UE1 defined by the RRCconfigured SL data communication resources. This is similar totransmission 612 to UE2. At 622, the SA of TB2 is decoded by UE3, andthe SL data of TB2 is decoded at 624 based on the decoded SA.

The data shown at 606 and/or 626 could have been received from the BS ornetwork 600 or another source, or generated by UE1. In the case thatdata is received by UE1 and intended for UE2 or UE3, transmissions 612,616 may be a retransmission of that data. As noted above, data fortransmission might not necessarily be received by UE1 from anothercomponent. The BS or network 600 is only one example source of data thatmay be transmitted between UEs over a sidelink. Regardless of the datasource, SA and SL data transmissions as shown in FIG. 6A are performedwhen UE1 determines that it has data to send to UE2 and/or UE3.

FIG. 6B is another signal flow diagram illustrating an example of adistributed grant-free transmission mode for SL communications, in anexample system with a BS or network 600 and UE1 to UE3. In FIG. 6B, at630 UE1 selects a transmission pattern from a transmission pattern pool.Transmissions 602, 610, 612, 614, 616 correspond to similarly labeledtransmissions in FIG. 6A. Similarly, decoding operations 618, 620, 622and 624 correspond to similarly labeled decoding operations in FIG. 6A.FIG. 6B also includes RRC configuration transmission 628.

In transmission 628 from the BS or network 600 to UE1, RRC signalingconfigures SL data communication resources and SL control resources. Atransmission pattern pool is included in the configuration of SL datacommunication resources in this example. This is different fromtransmission 604 of FIG. 6A, where a transmission pattern is optionallyincluded in the configuration of SL data communication resources. In RRCconfiguration 628, UE1 may also be optionally configured with a startingtime location and optionally a periodicity for the transmission patternsfor the transmission pattern pool. As also described herein, an exampleof configuration of a transmission pattern pool in the time domain caninclude an indication of repetition number and length of thetransmission patterns in the transmission pattern pool. The transmissionpattern pool may also include information indicating the range andpartition of frequency domain subchannels. Optionally, a transmissionpattern pool may also be included in the configuration of SL controlresources. In some embodiments, SL control resources may also be derivedfrom SL data resources. This transmission pattern pool may be the sameas or different from the transmission pattern configured for SL datacommunication resources. In some other embodiments, transmission patternpool may be indicated in broadcast signaling (e.g. in system informationblock (SIB)).

As an example of RRC configuration signaling for transmission pool in604, consider a UE that is to be configured with a transmission patternpool shown in FIG. 1K. The RRC configuration may include optionally thelength of the transmission pattern, which is 5 slots, a repetitionnumber K, which is 2, an RV sequence associate with repetitions of theTB, which is {0 3 0 3} or {0 3} indicating the first transmission useRV0 and second transmission use RV3, a starting time location of thetransmission pattern or initial transmission, which is the starting timelocation of T0, and a periodicity of the transmission pattern. The RRCconfiguration may further include the starting RB of the first frequencysubchannel, which is the starting RB of F0, the number of frequencysubchannels, which is 4, and the number of RBs for each frequencysubchannel, which is the frequency size or number of RBs in F0, F1, F2or F3. In one embodiment, any time domain transmission pattern with 2transmissions at two different slots within the 5 slots of T0 to T4 incombination with any frequency subchannel among F0, F1, F2 and F3 foreach transmission can be a valid transmission pattern to be selectedamong the transmission pattern pool. In another embodiment, only thetransmission pattern corresponding to the resources mapped to UE1 toUE10 as in FIG. 1K are consider a valid transmission pattern to beselected among the transmission pattern pool.

At 630, UE1 selects a transmission pattern for SL data transmission fromthe transmission pattern pool included in transmission 628. Thetransmission pattern may be selected autonomously by UE1. In someembodiments, the selection of the transmission pattern among thetransmission pattern pool may not be completely random. The selection in630 may be further based on one or more of the combination of thefollowing factors: 1) location, velocity, and direction of thetransmitter, distance between vehicles, 2) avoiding occupied resourcesand avoiding resource collision by selection of a transmission patternand/or resources by reading other UE's SA resources (to avoid usingsimilar resources) and sensing energy level of transmission thathappened earlier, 3) based on measurement results such as measurement ofreference signal received power (RSRP) of PSSCH, measurement of channelbusy ratio (CBR) (such that it does not over a certain limit), etc.Alternatively, UE1 may select the transmission pattern according to a UEindex previously assigned to the UE. The transmission pattern selectedby UE1 is used in transmissions 612, 616. In some embodiments, UE1 couldselect a transmission pattern for SL SA transmissions 610, 614. Thisselection may be made from the same transmission pattern pool used forSL data transmissions, or a different transmission pattern pool. Thetransmission pattern selected for SL control could be the same as ordifferent from the transmission pattern that is selected for SL datatransmissions.

FIG. 7 is a block diagram illustrating an example of an semi-persistentscheduling (SPS) signaled transmission pattern for an SL transmissionscheme. FIG. 7 includes an SL channel 700, RRC signaling 702, physicaldownlink control channel (PDCCH) by an SL UE ID, e.g. SL semi-persistent(SPS) vehicle radio network temporary identifier (V-RNTI) (i.e., a DCIsent with CRC scrambled by SPS-V-RNTI) 704, and communication resources706, 708, 710, which include resources for SA and PSSCH. In FIG. 7, SAand PSSCH are multiplexed (frequency division multiplexed for example)at the same time unit, but they can be located in different time units.

In FIG. 7, the communication resources 706, 708, 710 belonging to the SLchannel 700 are signaled by RRC signaling 702 and PDCCH by SL-SPS-V-RNTI704 through the DL. DCI signaling can be sent to the UE by a BS onPDCCH, with its CRC scrambled by SL-SPS-V-RNTI as shown at 704. Ingeneral, the RRC signaling indicates periodicity between adjacent timeresources or transmission patterns and the DCI signaling indicates thetransmission pattern and/or communication resources for one transmissionor multiple transmissions of a TB. The communication resources 706, 708,710 may be used for an SA (or a PSCCH) and a physical SL shared channel(PSSCH).

FIG. 8 is a signal flow diagram illustrating an example of SLtransmission mode using SPS. FIG. 8, like FIG. 7, involves SPS and DCIsignaling. In FIG. 8, scheduling of the transmission pattern for UE1 issemi-persistent. FIG. 8 includes BS or network 800 and UE1 to UE3.Transmissions 802, 810, 812, 814 and 816 correspond to similartransmissions 602, 610, 612, 614 and 616, respectively, in FIG. 6A.Similarly, decoding operations 818, 820, 822, 824 correspond to similardecoding operations 618, 620, 622, 624, respectively, in FIG. 6A.Operations 806 and 826 are similar to operations 606 and 626,respectively, in FIG. 6A. FIG. 8 also illustrates optional RRCconfiguration transmission 804, DCI activation transmission 805.

In optional transmission 804 from the BS or network 800 to UE1, RRCsignaling may optionally configure an RP for SL communication. The RRCsignaling may also configure part of the resources used for thetransmission patterns, e.g., a periodicity of transmission patterns.

In transmission 805 from the BS or network 800 to UE1, DCI signalingactivates a transmission pattern in UE1. This activation could indicatea transmission pattern for UE1. The location of DCI may determine thestarting time location of the transmission pattern. The activation DCImay also include transmission parameters and resources used for thetransmission of SL data and control in 812 and 810. The transmissionpattern may be also defined without RP or in the RP defined through RRCsignaling. After the DCI activation, the transmission pattern is assumedto repeat itself periodically with periodicity between two adjacenttransmission patterns configured in RRC signaling in 804. In thisrespect, FIG. 8 may be considered to be a form of SL SPS. Afterdetermining the transmission pattern and periodicity, UE1 transmitsusing transmissions 810, 812, 814, 816 in the same manner as describedabove in reference to FIG. 6A.

Other embodiments could also involve DCI. FIG. 9 is signal flow diagramillustrating an example of an SL scheduled transmission scheme. In FIG.9, scheduling of the transmission pattern for UE1 is dynamic. FIG. 9includes BS or network 900, UE1 and UE2. Transmissions 902, 910 and 912correspond to similar transmissions 602, 610 and 612, respectively, inFIG. 6A. Similarly, decoding operations 918, 920 correspond to similardecoding operations 618 and 620, respectively, in FIG. 6A. FIG. 9 alsoincludes optional RRC configuration transmission 904, which correspondsto a similar transmission described above with reference to FIG. 8.Transmission 904 may optionally include resource configuration of an RP.Transmission 904 may or may not include a periodicity as illustrated inFIG. 8. Additionally, transmission 906 for DCI scheduling isillustrated.

In transmission 906 from the BS or network 900 to UE1, the DCI schedulesa dynamic SL transmission pattern for UE1. In the case that RRCconfiguration has configured an RP for SL communication usingtransmission 904, the DCI determines a transmission pattern for UE1 fromthat RP. Alternatively, the DCI includes a transmission pattern withoutan RP being configured. A repetition pattern or other transmissionpattern could be assigned to UE1 for each TB used in transmissions 910and 912. In this sense, the scheduling is dynamic. The starting locationof the transmission pattern may be determined by the time the DCI isreceived in 906.

FIG. 10 is a signal flow diagram illustrating an example of a UEcooperation using SL transmission. In FIG. 10, BS or network 1000 andUE1, UE2 are illustrated. FIG. 10 includes several transmissions,including DCI signaling 1002/1004 that is used to schedule the DLunicast or multicast data transmission 1006/1008, optional SAtransmission 1010, and retransmission of the TB from 1006, at 1012. FIG.5F also includes decoding at 1014.

In transmission 1002/1004 a DCI used for scheduling DL unicast ormulticast transmission is transmitted from the BS or network 1000 to UE1and UE2. The DCI used for DL unicast or multicast transmission mayfurther include information for SL retransmission resources for UEcooperation. As an example, the DCI in 1002 may include a startinglocation (e.g. a starting slot) of a transmission pattern. The DCI couldbe a group common (GC)-PDCCH.

In transmission 1006/1008 a TB is transmitted from the BS or network1000 to UE1 and UE2 in multicast transmission, or just UE1 in the caseof unicast transmission.

In optional transmission 1010, an SA is transmitted from UE1 to UE2. Insome embodiments, it might not be necessary to transmit an SA from UE1to UE2 and the transmission at 1010 might not be performed.

In transmission 1012, the TB from 1006 is retransmitted from UE1 to UE2.The retransmission in the SL at 1012 may use SL transmission resourcesconfigured by UE specific RRC signaling beforehand, or configured by theDCI signaling in 1002 or a combination of RRC signaling and the DCIsignaling sent in 1002. For example, UE may use the resources configuredin RRC, which may include a transmission pattern, a starting location(offset) and a periodicity of the transmission pattern. Alternatively,UE may use the transmission pattern configured by the RRC and use thestarting location configured in the DCI signaling in 1002 as shown inFIG. 10. In other embodiments, the transmission pattern may also beindicated in the DCI. At 1014, the data is decoded from the SLtransmission 1010 and the DL unicast or multicast 1008.

The retransmission in FIG. 10 is an example of UE cooperation, as UE2might not have been able to properly decode transmission 1008, forexample, if UE2 is out of range of the BS or network 1000. However, UE2could be able to decode the retransmission from UE1 on the SL.Alternatively, UE2 may decode the retransmission 1012 from UE1 andcombine the retransmission with the original transmission received fromDL transmission 1008. In this sense, UE1 may be considered a CUE, andUE2 may be considered a TUE.

Several embodiments disclosed herein may involve control signalingbetween UEs. FIGS. 6A, 6B, and 8, for example, illustrate SAtransmissions. Different SA configurations are possible.

FIG. 11A is a plot illustrating an example of a configuration of an SA.FIG. 11A illustrates time slots 1100-1106 on a time-frequency resourcegrid. During four of those time slots 1101, 1103, 1105 and 1106, an SAtransmission and an SL data transmission are performed. Thesetransmissions may be performed, for example, in accordance with atransmission pattern.

In FIG. 11A, an SA is associated with each of the four SL transmissionsin the time slots 1101, 1103, 1105 and 1106, which correspond to atransmission pattern {0101011} that is used as an example above. Each SAmay indicate the transmission pattern and resources used for each SLdata transmission of time slots 1101, 1103, 1105 and 1106 (may includeboth time domain and frequency domain configuration described earlier).An SA may also include the number of transmissions, and the RV sequenceassociated with the transmissions. Each SA may also indicate thestarting location of the transmission pattern or the time location ofthe transmission associated with this SA (the indication can be actualtime location or relative time location to the SA). In the case of an SAand its associated SL transmission being frequency division duplexed(FDDed) as in FIG. 11A or otherwise combined in the same time unit, thetime location of the associated SL transmission may be derived from thetime location of the SA. Additionally, the SAs may indicate otherinformation associated with the transmissions of SL data such as the RVfor each SL transmission and/or the RV for its associated transmission.An SA may also indicate which transmission of the TB and/or RV for thistransmission. For example, the SA in slot 1101 may indicate that this isthe first transmission of the TB and it may also indicate the RV that isassociated with this TB. Alternatively, each SA may only include thetransmission pattern and resources used for the SL transmission for theassociated transmission. For example, the SA transmission associatedwith time slot 1101 may only include the parameters used for the SL datatransmission in that particular time slot 1101.

FIG. 11B is another plot illustrating an example of a configuration ofan SA. FIG. 11B illustrates the same time slots as FIG. 11A. However, anSA transmission is performed only in time slot 1101, and is associatedwith all transmissions in the transmission pattern. Therefore, the SAtransmitted during time slot 1101 in FIG. 11B includes the transmissionpattern and resources used for each SL data transmission in time slots1101, 1103, 1105 and 1106 (may include both time domain and frequencydomain configuration described earlier). An SA may also include thenumber of transmissions for the TB, and the RV sequence associated withthe transmissions. The SA may also indicate the starting time locationof the transmission pattern or the starting time location of the initialtransmission of the TB. In some embodiments, an SA may use its own timelocation as reference and only include a time gap between the SA and thecorresponding data transmission (initial transmission of a TB, thestarting location of the transmission pattern or the data transmissionassociated with the SA) instead. In the case of SA and its associated SLtransmission being FDDed as in FIG. 11A or otherwise combined in thesame time unit, the time location of the associated SL transmissions maybe derived from the time location of the SA.

In FIGS. 11A and 11B, the SA and SL data transmissions are separatedusing frequency division duplex (FDD). In such a scenario, the timelocations of an SA may not need to be explicitly configured by the BS inthe example SL transmission modes described herein, as the time locationof an SA can be derived from the time location of its associated SL datatransmission/transmissions. However, in general, the SA and SL datatransmissions may be separated using other configurations, such timedivision duplex (TDD). In the case of TDD, an SA may include a time gapbetween the time location of the SA and the time location of itsassociated SL data transmission (in a configuration of FIG. 11A) or theSA may include a time gap between the time location of SA and the timelocation of the initial SL data transmission or the transmission patternof its associated data transmissions of the TB (in a configuration ofFIG. 11B). Similarly, in the case of TDD, when configuring the SAresource, the BS may indicate a similar time gap between SA and itsassociated data transmission such that a UE can derive the time resourceused for SA given the time resource configured for the datatransmission.

For the SA in the configurations of FIGS. 11A and 11B or an SA ingeneral, the SA may indicate the time and frequency resources used foreach SL transmission of the TB.

An SA may indicate the actual frequency location of each transmission.In one embodiment, SA may indicate the starting VRB or PRB and the sizeof frequency resources. Each transmission of the TB may share the samefrequency resource parameters. In the case of configuration based onVRB, the actual PRB may be derived based on frequency hoppingconfiguration for each transmission. In another embodiment, an SA mayindicate an index sequence of frequency subchannels used for eachtransmission, similar to the RRC configuration of frequency domainresources. An SA may further indicate the range and partition of thefrequency subchannels similar to the RRC configuration of frequencydomain resources, which may include the starting RB of the firstfrequency subchannel, the number of frequency subchannels, the number ofRBs for each frequency subchannel. Alternatively, the range andpartition of the frequency subchannels may be configured in systeminformation and common for all UEs. Alternatively, the range andpartition of the frequency subchannels may be configured in RRCsignaling for the receiving UE, where the same frequency subchannelpartition can be applicable to the transmitting UE. Similarly, an SA mayindicate the time location of each transmission by sending the timedomain transmission pattern bitmap. Alternatively or additionally, an SAmay send the time location of an initial transmission and/or a time gapbetween initial transmission and a repetition of the TB. The timelocation can be the actual time location or the time location relativeto the time location of SA transmission.

Distributed grant-free SL communication as described herein could beapplied to group based configurations. Groups may include one or moreCUEs and one or more TUEs. The process of group based configuration maybe performed as described below.

Before SL transmission, a discovery phase may be used to form thecooperation group. In a discovery phase, all potential CUEs and TUEs ina group may be signaled a group ID, for example, a group RNTI.

In a broadcast/multicast phase, a BS may schedule a DL multicast using agroup common (GC)-PDCCH (i.e. a GC-DCI) with cyclic redundancy check(CRC) scrambled by the group RNTI. The GC-PDCCH may also indicate thestarting time unit (e.g. slot) for a cooperation phase. Alternatively,if the transmission is to start from a leader UE (LUE), then the LUE maysend a scheduling assignment (SA) along with an SL data transmission inthe SL unicast or multicast phase. The SA may indicate the starting timeunit (e.g. slot) for a cooperation phase.

In a cooperation phase, the CUEs retransmit the data that is received inthe DL/SL broadcast/multicast and send to the TUE. The CUEs use thestarting time location (e.g. a starting slot) of the initialtransmission or the transmission pattern, a transmission pattern andother resource configuration parameters associated with the UE for theSL transmission in the cooperation phase. The UE specific transmissionpattern and other resource configuration parameters may be configured inRRC signaling as described in this disclosure or associated with a UEindex among the group as described in the next paragraph. Alternativelyand/or additionally, the SL transmission resource for SL datatransmission in the cooperation phase may also be configured orpartially configured by the DCI sent by the BS or SA sent by the LUE inthe multicast/broadcast phase. For example, a CUE can use the startingtime location indicated in the multicast/broadcast phase along with itstransmission pattern configured by RRC to determine its transmissionresources for the cooperation phase. The CUE may also send an SA alongwith the data transmission to indicate the transmission resource for thetransmission in the cooperation phase. The SA can be associated with orcontain the information of the group RNTI.

Alternatively, the UE may be provided with a UE index among the group,which is associated with communication resources (for example, timedomain transmission pattern, RV sequence, frequency-domain resources,DMRS resources). The UE index may be configured by RRC signaling alongwith the group-RNTI. The UE index may be assigned in the discovery phaseof forming the UE cooperation group. A UE may be configured with atransmission pattern pool. The transmission pattern pool may beconfigured or predefined to be common for all the UEs in the samecooperation group. Alternatively, the transmission pattern pool can beUE specifically configured. The transmission pattern pool may beconfigured beforehand for the group, e.g. in the discovery phase.Alternatively, the transmission pattern pool may be indicated during thebroadcast/multicast phase in the DCI or SL control channel. For example,a BS or network could indicate a repetition number and length oftransmission pattern in the GC-PDCCH used in the broadcast phase, whichdefines the transmission pattern pool as described earlier in thisdisclosure. The transmission pattern can also be predefined withoutsignaling. During the cooperation phase, the UE maps the UE index to atransmission pattern pool to determine its transmission pattern.

FIGS. 1K and 2 provide examples of a transmission pattern pool, as wellas mapping of UE indices to transmission patterns within thetransmission pattern pool.

In some embodiments, in the cooperation phase, every CUE may beforwarding the same packets to all other UEs. If different UEs aresending the same packets over the same frequency-domain resources, areceiving UE can combine the different signals to decode the packetstogether. The UEs may also use the whole bandwidth for jointtransmission using the same RV (e.g. as shown in FIG. 2, where eachvertical partition is assumed to occupy the whole bandwidth while onlythe time domain pattern is shown in FIG. 2) or orthogonal resources fordifferent RVs.

FIG. 12 is a block diagram illustrating an example of a group basedconfiguration for distributed grant-free SL transmission in a network.FIG. 12 includes multiple CUEs 1200, identified as CUE1 to CUEn, and oneTUE 1202. FIG. 12 also includes a BS or leader UE (LUE) 1204. In thecase that the transmission starts with the BS 1204, a DCI 1206 and a DLbroadcast 1208 are transmitted. In the case that the transmission startswith the LUE 1204, an SA 1206 and an SL broadcast 1208 are transmitted.FIG. 12 further illustrates RRC signaling 1210, a SL retransmissionresource 1212, and a UE specific transmission pattern 1214.

If the transmission starts at a BS at 1204, then the BS sends the DCI1206, which is used for scheduling a DL broadcast transmitted from theBS 1204 to CUEs 1200. The BS then transmits a DL broadcast 1208 of adata block to CUEs 1200.

Alternatively, if the transmission starts at an LUE at 1204, the LUEsends an SA 1206, which is used for scheduling a SL broadcasttransmitted from the LUE 1204 to CUEs 1200. The LUE then transmits a SLbroadcast 1208 of a data block.

The RRC signaling 1210 configures the UE specific transmission pattern1214 to each of the CUEs 1200. The CUE may optionally indicate itstransmission pattern in the cooperation phase to the TUE in an SAtransmission.

As described in FIG. 12, the DCI 1206 may indicate SL retransmissionresources for UE cooperation. As an example, the DCI in 1206 may includea starting location (e.g. a starting slot) of the transmission pattern1214.

After receiving the UE specific transmission pattern 1214, and possiblythe SL retransmission resource 1212, the CUEs may optionally inform theTUE of the transmission pattern 1214 using an SA. The CUEs 1200 may thenretransmit the received data block from the DL/SL broadcast 1208 to theTUEs 1202 using the communication resource slots included in thetransmission pattern and possibly the SL retransmission resource 1212.For example, the CUE may use the starting time location or starting slotindicated in the DCI/SA in 1206 together with the transmission patternconfigured in RRC signaling to determine the resources used toretransmit the data block received from the BS/LUE in the DL/SLmulticast. Alternatively, the CUE may use the transmission pattern andstarting time slot that are configured in RRC signaling for the SLretransmission of the data block.

In other embodiments, RRC (UE specific or cell specific) or SIBsignaling configures or predefines a transmission pattern pool, and a UErandomly selects a transmission pattern from within the transmissionpattern pool. A common transmission pattern pool can be defined forRRC_idle and RRC_inactive UEs.

In some embodiments, the RRC or SIB signaling configures the length ofthe transmission pattern and the repetition number (K) of the pattern.The UE randomly selects one of the transmission patterns among all thepossible patterns of the transmission pattern pool.

For some configurations, the UE could randomly select a frequencysubchannel among all predefined frequency subchannels. UE could furtherrandomly select a signature, codebook or layer among all codebooks forNOMA transmission.

For some other configurations, the UE could randomly select atransmission pattern among a transmission pattern pool which includes acombination of resources in different dimensions. As described above, acombination of two or more of time-domain, frequency-domain, DMRS, layerand other resources could be configured together using a single UEindex.

In the case of group based configuration, if there is a mapping betweenthe UE index and a combination of communication resources as describedabove, UE may be able to randomly select a UE index which maps to one ofthe communication resource combinations.

Various features of distributed GF SL communications are describedabove. Method embodiments will now be described in more detail.

FIG. 13 is a flow diagram illustrating an example of a method 1300 forsidelink communications. The example method 1300 is illustrative of amethod performed by a user equipment (UE), and involves receiving at1302, by the UE, a message indicating a sidelink (SL) communicationresource configuration. The configuration indicated in the message is tobe used by the UE for SL control information and SL data communicationsbetween the UE and another UE. The SL data communications could bebetween the UE and multiple other UEs.

In some embodiments, the configuration includes one or more transmissionpatterns. For example, the SL communication resource configuration coulddefine a transmission pattern pool that includes multiple transmissionpatterns. The transmission patterns could define how communicationresources are to be used for SL control, SL data transmissions, or both.

The SL communication resource configuration could define a transmissionpattern for transmitting SL control information. Optionally, a methodcould include identifying, at 1304, a transmission pattern for SLcontrol information from a transmission pattern pool. This could involvethe UE selecting the transmission pattern from the pool. Thetransmission pattern and/or pool for transmitting the SL controlinformation could be the same as or different from a transmissionpattern and/or pool for transmitting the SL data communication.

The example method 1300 also involves transmitting at 1306, by the UE,SL control information according to the SL communication resourceconfiguration. This SL control information could be transmitted to oneUE or to multiple UEs. The SL control information may indicate therepetition pattern defined by the SL communication resourceconfiguration. The transmitting at 1306 could also be performed inaccordance with a transmission pattern for the SL control information,if configured. In some embodiments, transmitting the SL controlinformation includes transmitting, by the UE, a scheduling assignment(SA) to another UE using a communication resource defined in the SLcommunication resource configuration, and the SA indicates communicationresources used for transmitting the SL data communication. In furtherembodiments, the transmitting at 1306 also includes transmitting oneinstance of the SL control information for both the initial transmissionof the data block and the repetition of the data block. For example, asillustrated in FIG. 11B, a single SA could be transmitted for theinitial transmission of the data block and the repetition of the datablock. The transmitting at 1306 could also include transmitting aseparate instance of the SL control information for each of the initialtransmission of the data block and the repetition of the data block.This is illustrated in FIG. 11A, for example.

As noted above, in some embodiments the SL communication resourceconfiguration includes a transmission pattern that defines a pattern fortransmitting the SL data communication. The transmission pattern coulddefine an initial transmission of a data block and a repetition of thedata block. The transmission pattern could further define time resourcesused for the initial transmission of the data block and the repetitionof the data block. The SL communication resource configuration couldfurther include a starting time of the transmission pattern, and thetransmission pattern further defines a time gap from the initialtransmission of the data block to the repetition of the data block.

The communication resource configuration could include a transmissionpattern pool that includes multiple transmission patterns. As shown at1308, a method 1300 could include identifying the transmission patternfor SL data communication, from such a transmission pattern pool.

For example, the UE could belong to a UE group and the transmissionpattern pool could include a transmission pattern pool configured forthe UE group. In these embodiments, the UE could identify a transmissionpattern from among the transmission patterns of the transmission patternpool for the UE group. Identifying the transmission pattern couldinclude identifying the transmission pattern based on a UE index of theUE, and a method could then involve receiving additional signalingassigning the UE index to the UE for example. Such additional signalingcould include downlink control information (DCI) signaling.

Identifying the transmission pattern at 1308 could involve the UEselecting the transmission pattern. The transmission pattern selectionby the UE could be random by UE. Other selection embodiments are alsodisclosed herein.

FIG. 13 illustrates optional transmission pattern identifications at1304, 1308. In some embodiments, one or more other UEs use differenttransmission patterns.

The example method 1300 also involves transmitting at 1310, by the UE,an SL data communication according to the SL communication resourceconfiguration This SL data communication could be transmitted to one UEor to multiple UEs. In some embodiments, the SL data communicationincludes a retransmission of a data communication.

In the example method 1300, the SL control information and the SL datacommunication are transmitted by the UE, at 1304 and 1308, respectively,without receiving, in a downlink control information (DCI), a grant ofcommunication resources.

The example illustrated in FIG. 13 is represents one possibleembodiment. However, other embodiments are also possible which couldinclude additional features, fewer features, and/or different featuresthan those illustrated in FIG. 13.

For example, FIG. 13 illustrates transmitting an SL data communicationat 1310. In some embodiments, a UE listens for SL transmissions by otherUEs during segments of a transmission pattern during which it is notperforming SL transmissions.

In further embodiments, the SL communication resource configurationdefines communication resources used for transmitting the SL controlinformation or the SL data communication. The communication resourcescould include at least one of time-domain resources, frequency-domainresources and code-domain resources.

The present disclosure also provides various options for performing theillustrated operations. The message received at 1302, indicating the SLcommunication resource configuration, could be a radio resource control(RRC) message. Another possible option would be a Medium Access Controllayer Control Element (MAC CE) message.

Embodiments are not in any way restricted to methods. System and deviceembodiments are also contemplated.

FIG. 14 is a block diagram illustrating an example of atelecommunications network 1400 according to one embodiment. Thetelecommunications network 1400 includes a core network 1402 and anaccess network 1406. The access network 1406 serves a plurality of UEs1404 a, 1404 b, 1404 c, 1404 d, 1404 e, 1404 f, 1404 g, 1404 h, and 1404i. The access network 1406 could be an Evolved Universal TerrestrialAccess (E-UTRA) network. As another example, the access network 1406could be a cloud access network (C-RAN). The access network 1406includes a plurality of BSs 1408 a, 1408 b, and 1408 c. The BSs 1408 a-ceach provide a respective wireless coverage area 1410 a, 1410 b, and1410 c. Each of the BSs 1408 a-c could be implemented using a radiotransceiver, one or more antennas, and associated processing circuitry,such as antenna radio frequency (RF) circuitry,analog-to-digital/digital-to-analog converters, etc.

Although not illustrated, the BSs 1408 a-c are each connected to thecore network 1402, either directly or through one or more centralprocessing hubs, such as servers. The BSs 1408 a-c could serve as agateway between the wireline and wireless portion of the access network1406.

Each one of BSs 1408 a-c may instead be referred to as a basetransceiver station, a radio BS, a network node, a transmit node, atransmit point, a Node B, an eNode B, or a remote radio head (RRH),depending upon the implementation.

In operation, the plurality of UEs 1404 a-i access thetelecommunications network 1400 using the access network 1406 bywirelessly communicating with one or more of the BSs 1408 a-c.

UEs 1404 a-d are in close proximity to each other. Although the UEs 1404a-d can each wirelessly communicate with the BS 1408 a, they can alsodirectly communicate with each other, as represented at 1416. Thecommunications represented at 1416 are direct communications between UEsthat do not go through an access network component, such as a BS. Asshown in FIG. 14, UE to UE communications 1416 are directly between theUEs 1404 a-d and are not routed through the BS 1408 a, or any other partof the access network 1406. Communications 1416 may also be referred toas lateral communications. In embodiments disclosed herein, UE to UEcommunications use an SL channel and an SL air interface. On the otherhand, a communication between an access network component, such as BS1408 a, and a UE, as in communication 1414, is called an accesscommunication. An access communication occurs over an access channel,which can be a UL or DL channel, and an access communication uses aradio access communication interface, such as a cellular radio accessair interface. Access and SL air interfaces may use differenttransmission formats, such as different waveforms, different multipleaccess schemes, and/or different radio access technologies. Someexamples of radio access technologies that could be used by an accessair interface and/or an SL air interface are: Long Term Evolution (LTE),LTE License Assisted Access (LTE-LAA), and WiFi.

By using the SL communications 1416, the UEs 1404 a-d may be able toassist with wireless communications between the UEs 1404 a-d and the BS1408 a. As one example, if UE 1404 c fails to correctly decode a packetreceived from the BS 1408 a, but if UE 1404 d is able to receive andcorrectly decode the packet from the BS 1408 a, then UE 1404 d coulddirectly transmit the decoded packet to UE 1404 c using SLcommunications 1416. As another example, if UE 1404 c moves out ofwireless coverage area 1410 c, such that UE 1404 c can no longerwirelessly communicate with the BS 1408 a, then UE 1404 b could forwardmessages between the UE 1404 c and the BS 1408 a. As another example, UE1404 a and UE 1404 c could both receive a signal transmitted from the BS1408 a that carries a packet meant for UE 1404 c. UE 1404 a may thentransmit to UE 1404 c, via SL communications 1416, the signal asreceived by UE 1404 a. UE 1404 c may then use the information receivedfrom UE 1404 a to help decode the packet from the BS 1408 a. In theseexamples, capacity and/or coverage may be enhanced through theassistance of UEs 1404 a, 1404 b, and/or 1404 d. V2X communications asreferenced herein are an example of SL communications.

The UEs 1404 a-d form a UE group 1420. The access network 1406 couldassign a group identifier (ID) to the UE group 1420. The UE group ID mayallow the access network 1406 to address the UE group 1420 as a wholeand distinguish the UE group 1420 from other UE groups. The UE group IDmay also be used to broadcast information within the UE group, i.e.address all other UEs within the UE group 1420. The UE group 1420 mayform a logical or virtual device mesh in which the members of the UEgroup 1420 communicate amongst themselves using UE communications overan SL air interface, but the UE group 1420 as a whole acts as a singledistributed virtual transceiver with respect to the access network 1406.The UE group ID may be a group radio network temporary identifier(G-RNTI), for example.

When a particular UE in the UE group 1420 is being assisted or is to beassisted with wireless communication between that UE and the BS 1408 a,then that particular UE is referred to as the target UE. In the examplesabove, UE 1404 c is being assisted and so is the TUE 1404 c. The otherUEs 1404 a, 1404 b, and 1404 d in the group 1420 form a cooperationcandidate set, which is a set of UEs that may cooperate to help the TUE1404 c. The subset of UEs in the cooperation candidate set that actuallyassist the target UE 1404 c form a cooperation active set. Thecooperation active set may be dynamically selected to assist the targetUE 1404 c. The UEs in the cooperation active set are referred to ascooperating UEs (CUEs). In UE group 1420, UEs 1404 a, 1404 b, and 1404 dform the cooperation candidate set. If UEs 1404 a and 1404 b actuallyassist target UE 1404 c, then UEs 1404 a and 1404 b form the cooperationactive set and are the CUEs. As UEs 1404 a-d move around, some may leavethe UE group 1420 and/or other UEs may join the UE group 1420.Therefore, the cooperation candidate set may change over time, e.g., thecooperation candidate set may change semi-statically. The UE group 1420may also be terminated by the network 1406, e.g., if the networkdetermines that there is no longer a need or opportunity for the UEgroup 1420 to provide assistance in wireless communication between theBS 908 a and members of the UE group 1420.

There may be more than one UE group. For example, UEs 1404 e and 1404 fin FIG. 14 form another UE group 1422.

FIG. 15 is a block diagram illustrating an example of a network 1552serving two UEs 1554 a and 1554 b, according to one embodiment. Thenetwork 1552 may be the access network 1406 from FIG. 14, and the twoUEs 1554 a and 1554 b may be two of the four UEs 1404 a-d in FIG. 14, orthe UEs 1554 a and 1554 b may be UEs 1404 e and 1404 f in FIG. 14.However, more generally this need not be the case, which is whydifferent reference numerals are used in FIG. 15.

The network 1552 includes a BS 1556 and a managing module 1558. Themanaging module 1558 instructs the BS 856 to perform actions. Themanaging module 858 is illustrated as physically separate from the BS1556 and coupled to the BS 1556 via a communication link 1560. Forexample, the managing module 1558 may be part of a server in the network1552. Alternatively, the managing module 1558 may be part of the BS1556.

The managing module 1558 includes a processor 1562, a memory 1564, and acommunication module 1566. The communication module 1566 is implementedby the processor 1562 when the processor 1562 accesses and executes aseries of instructions stored in the memory 1564, the instructionsdefining the actions of the communication module 1566. When theinstructions are executed, the communication module 1566 causes the BS1556 to perform the actions described herein so that the network 1552can establish, coordinate, instruct, and/or control a UE group.Alternatively, the communication module 1566 may be implemented usingdedicated circuitry, such as an application specific integrated circuit(ASIC) or a programmed field programmable gate array (FPGA).

The UE 1554 a includes a communication subsystem 1570 a, two antennas1572 a and 1574 a, a processor 1576 a, and a memory 1578 a. The UE 1554a also includes a communication module 1580 a. The communication module1580 a is implemented by the processor 1576 a when the processor 1576 aaccesses and executes a series of instructions stored in the memory 1578a, the instructions defining the actions of the communication module1580 a. When the instructions are executed, the communication module1580 a causes the UE 1554 a to perform the actions described herein inrelation to establishing and participating in a UE group. Alternatively,the module 1580 a may be implemented by dedicated circuitry, such as anASIC or an FPGA.

The communication subsystem 1570 a includes processing andtransmit/receive circuitry for sending messages from and receivingmessages at the UE 1554 a. Although one communication subsystem 1570 ais illustrated, the communication subsystem 1570 a may be multiplecommunication subsystems. Antenna 1572 a transmits wirelesscommunication signals to, and receives wireless communications signalsfrom, the BS 1556. Antenna 1574 a transmits SL communication signals to,and receives SL communication signals from, other UEs, including UE 1554b. In some implementations there may not be two separate antennas 1572 aand 1574 a. A single antenna may be used. Alternatively, there may beseveral antennas, but not separated into antennas dedicated only to SLcommunication and antennas dedicated only to communicating with the BS1556.

SL communications could be over Wi-Fi, in which case the antenna 1574 amay be a Wi-Fi antenna. Alternatively, the SL communications could beover Bluetooth™, in which case the antenna 1574 a may be a Bluetooth™antenna. SL communications could also or instead be over licensed orunlicensed spectrum.

The UE 1554 b includes the same components described above with respectto the UE 1554 a. That is, UE 1554 b includes communication subsystem1570 b, antennas 1572 b and 1574 b, processor 1576 b, memory 1578 b, andcommunication module 1580 b.

The UE 1554 a is designated as a target UE (TUE) and will therefore becalled TUE 1554 a. The UE 1554 b is a cooperating UE and will thereforebe called CUE 254 b. The CUE 1554 b may be able to assist with wirelesscommunications between the BS 1556 and TUE 1554 a if a UE group were tobe established that included TUE 1554 a and CUE 1554 b. Othercommunication scenarios are also contemplated, in a V2X application, forexample.

UE 1554 a may be specifically chosen as the target UE by the network1552. Alternatively, the UE 1554 a may itself determine that it wants tobe a target UE and inform the network 1552 by sending a message to theBS 1556. Example reasons why UE 1554 a may choose or be selected by thenetwork 1552 to be a target UE include: low wireless channel qualitybetween the UE 1554 a and the BS 1556, many packets to be communicatedbetween the BS 1556 and the UE 1554 a, and/or the presence of acooperating UE that is a good candidate for helping with communicationsbetween the BS 1556 and the UE 1554 a.

UE 1554 a need not always stay a target UE. For example, UE 1554 a maylose its status as a target UE once there is no longer a need or desirefor assistance with wireless communications between UE 1554 a and the BS1556. UE 1554 a may assist another target UE that is a cooperating UE ata later time. In general, a particular UE may sometimes be a target UEand other times may be a cooperating UE assisting another target UE.Also, sometimes a particular UE may be both a target UE receivingassistance from one or more cooperating UEs and also a cooperating UEitself assisting another target UE. In the examples below, the UE 1554 aacts only as a target UE, i.e., TUE 1554 a, and the UE 1554 b is acooperating UE to the TUE 1554 a, i.e., CUE 1554 b.

FIGS. 14 and 15 illustrate systems in which embodiments could beimplemented. In some embodiments, a UE includes a processor, such as1576 a, 1576 b in FIG. 15, and a non-transitory computer readablestorage medium, such as 1578 a, 1578 b in FIG. 15, storing programmingfor execution by the processor. A non-transitory computer readablestorage medium could also or instead be provided separately, as acomputer program product.

In such embodiments, programming could include instructions to: receive,by the UE, a message indicating a sidelink (SL) communication resourceconfiguration to be used by the UE for SL control information and SLdata communications between the UE and another UE; transmit, by the UE,SL control information according to the SL communication resourceconfiguration; and transmit, by the UE, an SL data communicationaccording to the SL communication resource configuration, wherein the SLcontrol information and the SL data communication are transmitted by theUE without receiving, in a downlink control information (DCI), a grantof communication resources.

The instructions to transmit the SL control information could includeinstructions to transmit, by the UE, a scheduling assignment (SA) to theother UE using a communication resource defined in the SL communicationresource configuration, the SA indicating communication resources usedfor transmitting the SL data communication.

The SL communication resource configuration could include a transmissionpattern that defines a pattern for transmitting the SL datacommunication.

The transmission pattern could define an initial transmission of a datablock and a repetition of the data block, and could also define timeresources used for the initial transmission of the data block and therepetition of the data block.

An SL communication resource configuration could include a starting timeof the transmission pattern, and the transmission pattern could furtherdefine a time gap from the initial transmission of the data block to therepetition of the data block.

Instructions to transmit the SL control information could includeinstructions to transmit one instance of the SL control information forboth the initial transmission of the data block and the repetition ofthe data block.

In some embodiments, the instructions to transmit the SL controlinformation include instructions to transmit a separate instance of theSL control information for each of the initial transmission of the datablock and the repetition of the data block.

The programming could also include instructions to listen for SLtransmissions by other UEs during segments of the transmission patternother than the SL transmissions.

One or more other UEs may use a different transmission pattern.

The SL communication resource configuration could define a transmissionpattern pool that includes multiple transmission patterns, as disclosedherein. The programming could then include instructions to identify thetransmission pattern among the transmission patterns of the transmissionpattern pool.

For example, the UE could belong to a UE group and the transmissionpattern pool could include a transmission pattern pool configured forthe UE group. The instructions to identify the transmission patterncould then include instructions to identify the transmission patternbased on a UE index of the UE. The programming could also includeinstructions to receive additional signaling assigning the UE index tothe UE. The additional signaling could be downlink control information(DCI) signaling, for example.

The instructions to identify the transmission pattern could includeinstructions to select the transmission pattern. The selection of thetransmission pattern is random in some embodiments, but other selectionoptions are possible.

The SL communication resource configuration could define a transmissionpattern for transmitting the SL control information. The transmissionpattern for transmitting the SL control information could be the same ordifferent from the transmission pattern for transmitting the SL datacommunication.

The SL communication resource configuration could define communicationresources used for transmitting the SL control information or the SLdata communication, and the communication resources could include atleast one of time-domain resources, frequency-domain resources andcode-domain resources.

The received message indicating the SL communication resourceconfiguration could be a radio resource control (RRC) message asdisclosed by way of example herein, or another type of message such as aMedium Access Control layer Control Element (MAC CE) message.

Embodiments disclosed herein could be useful in mitigating effects ofthe SL half duplex constraint. Embodiments could also improve thelatency and reliability of SL transmissions using a UE specifictransmission pattern, and a distributed transmission mode that can bedesigned to enable all UEs in a cooperation group to communicate witheach other even if some transmissions are affected by collisions or thehalf duplex constraint, for example.

The grant-free transmission modes described herein may be used in NRother than in SL and V2X communication. For example, the grant-freetransmission modes may be applicable in unlicensed transmission.

Although the present invention has been described with reference tospecific features and embodiments thereof, various modifications andcombinations can be made thereto without departing from the invention.The description and drawings are, accordingly, to be regarded simply asan illustration of some embodiments of the invention as defined by theappended claims, and are contemplated to cover any and allmodifications, variations, combinations or equivalents that fall withinthe scope of the present invention. Therefore, although the presentinvention and its advantages have been described in detail, variouschanges, substitutions and alterations can be made herein withoutdeparting from the invention as defined by the appended claims.Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

Moreover, any module, component, or device exemplified herein thatexecutes instructions may include or otherwise have access to anon-transitory computer/processor readable storage medium or media forstorage of information, such as computer/processor readableinstructions, data structures, program modules, and/or other data. Anon-exhaustive list of examples of non-transitory computer/processorreadable storage media includes magnetic cassettes, magnetic tape,magnetic disk storage or other magnetic storage devices, optical diskssuch as compact disc read-only memory (CD-ROM), digital video discs ordigital versatile disc (DVDs), Blu-ray Disc™, or other optical storage,volatile and non-volatile, removable and nonremovable media implementedin any method or technology, random-access memory (RAM), read-onlymemory (ROM), electrically erasable programmable read-only memory(EEPROM), flash memory or other memory technology. Any suchnon-transitory computer/processor storage media may be part of a deviceor accessible or connectable thereto. Any application or module hereindescribed may be implemented using computer/processorreadable/executable instructions that may be stored or otherwise held bysuch non-transitory computer/processor readable storage media.

It should also be appreciated that features disclosed herein could beapplied to components other than those specifically referenced by way ofexample, such as V2X infrastructure components including RSUs (i.e., notjust eNBs and UEs). A roadside unit (RSU) is a stationary transportationinfrastructure entity (e.g., an entity which can transmit speednotifications) supporting V2X applications that can exchange messageswith other entities supporting V2X applications. An RSU is a logicalentity which in addition to supporting V2X applications can also providethe functionalities of a network entity (e.g., eNB, gNB, base station),in which case it may be referred to as an e/gNB-type RSU, or a UE, inwhich case it may be referred to as a UE-type RSU. Network featurestherefore may apply to e/gNB-type RSUs and UE features may apply toUE-type RSUs.

Multiple Configurations for Sidelink Grant-Free Transmission

Multiple configured/preconfigured grant-free SL transmissionconfigurations with different configuration parameters are beneficial inorder to address message characteristics of V2X services and supportdifferent types of service and traffic. As such, a UE can betransmitting sidelink packets from different traffic classes (QCIs) withdifferent latency and/or bit rate requirements for which a singleresource configuration/pre-configuration may not be enough.

In some of the embodiments described, a UE is configured with multiplegrant-free SL transmission configurations and the UE can select betweenthe multiple configurations for sidelink transmission. The multipleconfigurations can be configured by higher layer signalling, such as RRCsignalling, or can be pre-configured.

For example, the multiple configurations correspond to multiple sets oftransmission resources, such as multiple sets of transmission patterns.Then, the UE selects between which configuration to use. This can bedone based on various selection criteria. These might include traffictype, packet size, reliability target, latency target to name a fewexamples. Based on these criteria, the UE selects which configuration touse. In a simplest case, there can be a table lookup which maps criteriato configuration. These configurations can be signalled orpre-configured as before. In some embodiments, once the configuration isselected, the UE makes a selection of a SL transmission resource usingone of the methods described herein, which may rely upon sensingresource occupancy or sidelink control information and/orshort/long-term measurement. Thus, the UE can independently anddynamically select between different grant-free SL configurations.

In some embodiments, the UE makes a selection of which configuration touse only when the UE is out of network coverage, and at other times, thenetwork informs the UE of which configuration to use. Alternatively, theUE makes a selection of which configuration to use at any timeirrespective of whether the UE is in or out of network coverage.

An example is shown in FIG. 20. Shown is a first configuration thatconsists of a first pool of transmission patterns 1950 that have 2repetitions. Shown is a second configuration that consists of a secondpool of transmission patterns 1952 that have 3 repetitions. The UE canselect between the two configurations. In some embodiments, anindication of which configuration is being used by the transmitting UEis included in the SA.

FIG. 21 is a flowchart of a method provided by an embodiment of thedisclosure. The method is performed by a UE, and begins in block 2100adaptively selecting between at least two sidelink (SL) communicationresource configurations to be used by the UE for SL transmissions. Themethod continues in block 2102 with selecting a SL transmission resourcefor use in making a SL transmission to a target UE based on the selectedSL communication resource configuration. The method continues in block2104 with transmitting, by the UE, SL control information according tothe SL communication resource configuration. The method continues inblock 2106 with transmitting, by the UE, an SL data communicationaccording to the SL communication resource configuration, wherein the SLcontrol information and the SL data communication are transmitted by theUE without receiving, in a downlink control information (DCI), a grantof communication resources.

In embodiments of the present disclosure, one or more of the multipleconfigurations are preconfigured or signaled to the UE via RRCsignaling. Each configuration/pre-configuration may include or indicatevalues for one or more of the following parameters: periodicity, offset,SL transmission resource pattern, SL transmission resource pattern pool,time/frequency location of the pattern or pattern pool, andtime/frequency size of sub-channel.

Selection of Grant-Free Transmission Resource Based on Decoding ofSidelink Control Channel

In some of the embodiments described herein, for the purpose of a UE toUE sidelink transmission, the transmitting UE selects a transmissionpattern to use for the transmission.

For example, in the embodiment of FIG. 6B, UE1 makes such a selection at630. In the embodiment of FIG. 6B, the pool of possible patterns isconfigured via RRC configuration.

More generally, the transmitting UE1 is aware of the pool of possiblepatterns before making the selection. For example, the pool could bepre-configured. More generally still, the transmitting UE may be awareof transmission resources or a pool of SL transmission resources thatcan be selected for the purpose of sidelink transmission, referred tohereinafter as SL transmission resources. The pool of transmissionpatterns is one specific example of SL transmission resources.

In some embodiments, the resources that the UE can select between areconfigured based on a SL communication resource configuration. The SLcommunication resource configuration can be a pattern (one-dimensional,two-dimensional, also known as time-frequency repetition pattern, etc.),a pool of patterns, a repetition number. For example, the SLcommunication resource configuration could be pre-configured. Theconfigured/pre-configured SL communication resource configuration may beprovided by a device manufacturer or a network operator (e.g., via asubscriber identity module). The SL communication resource configurationmay be also provided by the network operator when a UE is in coverage ofa base station so that the SL communication resource configuration isavailable wherever the UE may be, such as when the UE moves out of thenetwork coverage.

In an embodiment of the invention, a transmitting UE makes a selectionof a SL transmission resource for the purpose of a sidelink transmissionbased on additional information obtained from decoding sidelink controlchannels. In some embodiments, this approach is performed only when theUE is out of network coverage. Alternatively, the approach can beemployed at any time irrespective of whether the UE is in or out ofnetwork coverage.

More specifically, whether the network is involved in scheduling asidelink transmission or not, a transmitting UE will inform thereceiving UE of resources it is using for the sidelink transmission viasidelink control channel (SCI). This can be, for example via previouslydescribed SCI, SA, using PSCCH, or some other mechanism. So, for everysidelink transmission, there is a corresponding resource indication on acorresponding sidelink control channel. Note that another UE maytransmit an SCI some of the time even when it does not have SL data totransmit. This can also be decoded by the transmitting UE and used toassist in making the selection of the SL transmission resource.

With this embodiment, a given transmitting UE monitors the sidelinkcontrol channels of other UEs, and through such monitoring learns of theresources that are being used for sidelink transmissions of other UEs.For example, a UE that is part of a group of UEs may only monitor theSCI resources of other UEs in the group. Alternatively, a UE may monitorall SCI resources configured/pre-configured for the UE. Based on thisinformation, the transmitting UE can make a more intelligent selectionof resources for its own sidelink transmission. In some embodiments, theresources for the sidelink control channels are known to the UE. Thisnecessitates that the control information be transmitted in a mannerthat allows UEs other than the receiver UE to decode it. For example,the control information can be transmitted in an open manner (readableby all UEs), or may be scrambled using a common ID known to a group ofUEs.

The sidelink control information may indicate resources being used for acurrent sidelink transmission, and/or future sidelink transmissions. Bymonitoring the sidelink control information transmitted by other UEs, atransmitting UE can learn which resources are being used for a currentsidelink transmission (based on current sidelink control informationthat indicates resources being used for a current sidelinktransmission), and/or the UE can learn which resources are being usedfor a current sidelink transmission based on previous sidelink controlinformation that indicated resources being used for a future sidelinktransmission that is aligned with the current transmission and/or the UEcan learn which resources are being used for a current sidelinktransmission based on previous sidelink control information thatindicated resources being used for a future sidelink transmission thatis not aligned with the current transmission.

Where the sidelink control information for another sidelink transmissionindicates a pattern from a pool of patterns, or a resource from a poolof resources, the transmitting UE for a sidelink transmission can avoidselection of that particular pattern/resource. With this approach,collisions can be avoided, and performance can be improved.

FIG. 16 is a flowchart of a method provided by an embodiment of thedisclosure. The method is performed by a UE, and begins in block 1600with decoding a sidelink (SL) control channel transmitted by another UEto ascertain SL control information transmitted by the another UE. Themethod continues in block 1602 with selecting a SL transmission resourcefor use in making a SL transmission to a target UE taking into accountthe ascertained SL control information. The method continues in block1604 with transmitting, by the UE, SL control information comprising ascheduling assignment (SA) indicating the selected transmissionresource. The method continues in block 1606 with transmitting, by theUE, an SL data communication according to the transmitted SL controlinformation using the selected SL transmission resource, wherein the SLcontrol information and the SL data communication are transmitted by theUE without receiving, in a downlink control information (DCI), a grantof communication resources.

Optionally, the UE may also perform this SCI decoding procedure in orderto independently and dynamically select between different grant-free SLconfigurations.

Selection of Grant-Free Transmission Resource Based on Long-TermSidelink Measurement

FIG. 17 is a flowchart of a method provided by another embodiment of thedisclosure. The method is performed by a UE, and begins in block 1700with the UE measuring sidelink (SL) transmission resources in order toascertain sidelink resource occupancy or load. The method continues inblock 1702 with selecting a SL transmission resource for use in making aSL transmission to a target UE taking into account the measurements. Themethod continues in block 1704 transmitting, by the UE, SL controlinformation comprising a scheduling assignment (SA) indicating theselected SL transmission resource. The method continues in block 1706with transmitting, by the UE, an SL data communication according to thetransmitted SL control information using the selected SL transmissionresource, wherein the SL control information and the SL datacommunication are transmitted by the UE without receiving, in a downlinkcontrol information (DCI), a grant of communication resources.

In specific embodiments, the measuring sidelink transmissions resourcesis performed on a long-term basis or a short-term basis. Detailedexamples are provided below.

Selection of Grant-Free Transmission Resource Based on Long-TermSidelink Measurement

In an embodiment of the invention, a transmitting UE makes a selectionof a transmission resource for the purpose of a sidelink transmission,based on additional information obtained from long-term sidelinkmeasurement. In some embodiments, this approach is performed only whenthe UE is out of network coverage. Alternatively, the approach can beemployed at any time irrespective of whether the UE is in or out ofnetwork coverage.

More specifically, whether the network is involved in scheduling asidelink transmission or not, a transmitting UE will monitor sidelinktransmission resources on an ongoing basis. This can involve monitoringa pool of possible transmission resources or a pool of transmissionpatterns, for example. For example, the UE may measure reference signalreceive power (RSRP) or reference signal receive quality (RSRQ) or someother characteristic of signals that might be present on the resources.The measurements may be averaged over a defined period of time togenerate a metric for each transmission resource. A higher metric for agiven resource is an indication that the given resource is more heavilyloaded on average. Then, the UE takes this information into account inmaking a selection for transmission.

In a specific example, the UE ranks the possible resources according tothe calculated metric, and selects the resource with the most favourablemetric (which can be the lowest or the highest depending on the natureof the metric). If the metric reflects some measure of average power,the UE would select the lowest metric, as this would reflect the leastloaded resource. In another embodiment, the UE can select, for examplerandomly, from any resource that has a metric below/above a predefinedthreshold. In another embodiment, the UE can select, for examplerandomly, from the top X percent of resources that has a metricbelow/above a predefined threshold where X can be a number less than100, typically 10 or 20.

A specific example will be described with reference to FIG. 1K. Here, onan ongoing basis, the UE monitors each of the four frequencies F1,F2,F3and F4, over the five time periods (which are assumed to repeat cycliclyin this example). A metric for each pattern is determined based on thismonitoring. For example, for the UE1 pattern, the transmitting UEmeasures on F1 during T0, and F3 during T1, and produces a metric forthe UE1 pattern by combining these measurements. Such measurements aredone for each of the patterns. The patterns are then ordered by metricand a pattern is selected based on the ordering. The decision may bebased on the metric determined for measurements over a specified windowof time, for example over a configured number of time slots, or moregenerally a configured period of time (which can be configured in termsof a number of time slots or some other basis).

Optionally, the UE may also perform this long-term sensing procedure inorder to independently and dynamically select between differentgrant-free SL configurations.

Selection of Grant-Free Transmission Resource Based on Short-TermSidelink Measurement

In an embodiment of the invention, a transmitting UE makes a selectionof a transmission resource, for the purpose of a sidelink transmission,based on additional information obtained from short-term sidelinkmeasurement. In some embodiments, this approach is performed only whenthe UE is out of network coverage. Alternatively, the approach can beemployed at any time irrespective of whether the UE is in or out ofnetwork coverage.

More specifically, whether the network is involved in scheduling asidelink transmission or not, a transmitting UE will monitor SLtransmission resources on a short-term basis, just before making aselection of a resource for a sidelink transmission. This can involvemaking a short-term measurement of a pool of possible transmissionresources or pool of transmission patterns, for example. For example,the UE may measure energy levels across a specified frequency band(s).The UE may then perform a clear channel assessment (CCA) by comparingthe measured energy levels to a specified threshold. The short termmeasurement allows the UE to assess whether a given resource is beingused during a current transmission period. Then, the UE takes thisinformation into account in making a selection for a currenttransmission.

The measurements can, for example, be similar to those taken with listenbefore talk (LBT) protocols, which typically include a CCA procedure. Insome embodiments, the UE makes the short-term measurements for multipleresources, possibly all, and makes a selection based on themeasurements. This can involve determining which of the resources arenot being used for a current transmission period, and selecting betweenthose resources. In another embodiment, the UE makes an initialselection of a resource for transmission (possibly based on sidelinkcontrol information and/or long-term sidelink measurements) and thenmakes the short term measurement for the selected resource. If theresource is occupied as indicated by the short-term measurement, the UEmakes another selection, or waits a backoff time, for example a randombackoff time, before measuring the same resource again. Once the UEidentifies a resource not being used, the UE goes ahead with thetransmission using that resource.

A specific example will be described with reference to FIG. 1K. Assumethe UE has made an initial selection of pattern UE1. The UE makes ashort term measurement of the resources for UE1. If such measurementindicates the pattern is not being used, the UE can go ahead with thesidelink transmission using that pattern. If the short term measurementindicates that pattern is being used, the UE selects a different patternor waits a random backoff time before performing another short termmeasurement of the resources for UE1.

In some embodiments, the selection of a transmission resource forsidelink transmission is based on a combination of sidelink controlinformation and long-term sidelink measurement.

In some embodiments, the selection of a transmission resource forsidelink transmission is based on a combination of sidelink controlinformation and short-term sidelink measurement.

In some embodiments, the selection of a transmission resource forsidelink transmission is based on a combination of short-term sidelinkmeasurement and long-term sidelink measurement.

In some embodiments, the selection of a transmission resource forsidelink transmission is based on a combination of sidelink controlinformation, long-term sidelink measurement, and short-term sidelinkmeasurement.

Identification of occupied sidelink resources may be accomplished bymonitoring of transmission resources as described above, which can alsobe referred to as sensing. Sensing can include short-term measurementsand/or long-term measurements, as well as decoding sidelink controlchannel transmissions and detecting any other sidelink transmissions.

Optionally, the UE may also perform this short-term sensing procedure inorder to independently and dynamically select between differentgrant-free SL configurations.

Adaptive Adjustment of Grant-Free Resources Based on Sensing and/orDecoding of Sidelink Control Channel

In some embodiments, the resources available for SL transmission areadaptively adjusted in some manner based on the sensing and/or decodingof sidelink control channel. Note this is a distinct step compared toselecting the resource for sidelink transmission. In some embodiments,this approach is performed only when the UE is out of network coverage.Alternatively, the approach can be employed at any time irrespective ofwhether the UE is in or out of network coverage.

The adjustment may encompass adjusting one or a combination of: thenumber of repetitions;

the size of a transmission pattern;

the location of a transmission pattern;

some other parameter or combination of parameters.

For example, a UE may be configured with a set of patterns that includesa first subset that have a first number of repetitions, and a secondsubset that have a second number of repetitions. Based on the sensingand/or decoding of sidelink control channel, the UE can change thenumber of repetitions, by changing from selecting among the first subsetto selecting among the second subset.

Alternatively, the set of patterns may initially only include patternswith two repetitions, but the UE can extend each of those patterns toinclude three repetitions. Once the transmission resources are adjusted,the UE makes a selection for a given SL transmission based on theadjusted transmission resources.

A specific example is shown in FIG. 18A, where a first subset ofpatterns UE1, UE2, UE3 contain 2 repetitions, and a second subset ofpatterns UE4, UE5, UE6 contain 3 repetitions. Depending on sensingand/or decoding of sidelink control channel, the UE can select betweenthe first subset of the second subset.

Similarly, subsets of patterns can be defined which differ in size orlocation or some other parameter. An adjustment can be made by selectingfrom the appropriate subset of patterns.

Alternatively, starting with a pattern, or a pool of patterns, the UEcan make adjustments to the pattern or the pool of patterns to producean adjusted pool of patterns. Again this can, for example, involveadjusting the number of repetitions, size, location, or some otherparameter or combination of parameters of the selected pattern.

FIG. 19 is a flowchart of a method provided by an embodiment of thedisclosure. The method is performed by a UE, and begins in block 1900with decoding a sidelink (SL) control channel transmitted by another UEto ascertain SL control information transmitted by the another UE and/orperforming measurements on sidelink (SL) transmission resources. Themethod continues in block 1802 with adaptively adjusting a SLtransmission resource for SL transmission based on the decoding of theSL control channel and/or measurements on SL transmission resources. Themethod continues in block 1804 with transmitting, by the UE, SL controlinformation indicating the adaptively adjusted SL transmission resource.The method continues in block 1906 with transmitting, by the UE, an SLdata communication using the adaptively adjusted SL transmissionresource, wherein the SL control information and the SL datacommunication are transmitted by the UE without receiving, in a downlinkcontrol information (DCI), a grant of communication resources.

Information Contained in Sidelink Control Channel

For any of the embodiments described herein, the sidelink controlchannel may transmit a scheduling assignment which may include aresource allocation, such as a pattern indicator for a sidelinktransmission. In some embodiments, the sidelink control information alsoincludes: a power level for the sidelink transmission, an interferencemeasurement, and/or a spatial beam direction. This is included so thatother UEs (other than the target UE for that sidelink controlinformation) can observe the power level, and factor this in whenselecting a transmission resource for their own SL transmissions. Forexample, where the sidelink control information indicates a sidelinktransmission on a transmission resource with high power, this wouldweigh against selecting that transmission resource, possiblydisqualifying it from selection, in which case that resource isexcluded.

Flexibility in Starting Transmission

In some embodiments, a UE is constrained to start a transmission at thestart of a pattern. Irrespective of when a packet arrives fortransmission, the UE must wait for the beginning of the next patternbefore it can transmit. This approach can be applied to any of theembodiments described herein. For example, referring to FIG. 22, thetransmission pattern occurs within a block of 8 consecutive resources.The UE makes four repetitions for a given transmission within oneinstance of the transmission pattern. FIG. 8 shows two repetitions ofthe pattern 2010, 2012. If a packet is ready for transmission at T12014, the UE must wait until transmission pattern 2012 to transmit, andthe UE transmits using resources 2020, 2022, 2024, 2026.

In some embodiments, the UE is not constrained to start a transmissionat the start of a pattern. Rather, the UE can start transmission as soonas it is ready. The UE must still use the resources of the pattern, butcan start midway through the pattern. Referring again to FIG. 22, if apacket is ready for transmission at T1, the UE can transmit usingresources 2014,2016,2018,2020 instead of waiting to begin with resource2020 at the start of the next transmission pattern.

In some embodiments, no change to the SA is required to indicate exactlywhen, within a transmission pattern, the transmission begins. Forexample, where the resources defined in the SA are periodic/recurring, areceiving UE can monitor the resources and detect when the resources arebeing used for the transmission.

Alternatively, SA can include an indication of where the transmissionbegins. This can be an indication of the repetition number within a setof repetitions, an indication of the actual resource used for the firsttransmission, or an indication of a different pattern that reflects thedifferent start time.

This approach can be combined with any one or more of the otherembodiments described herein.

Resources for SL Transmission

In some embodiments, all the transmission patterns are composed of timefrequency regions for respective repetitions that have the same size intime and/or frequency. For example, in FIG. 18A, the different patternsare made up of time/frequency units that have the same dimension in timeand frequency. In another embodiment, one or more patterns within a poolcan be composed of time frequency regions that differ in the timedimension and or the frequency dimension, as shown in the FIG. 18B. Insome embodiments, a given pattern of a pool of patterns may be arecomposed of time frequency units of different sizes. These variationsare applicable to any of the embodiments described herein.

Resource Pools

A resource pool (RP) is a set of time and frequency resources that canbe used for SL transmission and/or reception. The time and frequencyresources in an RP can be contiguous or non-contiguous in either time orfrequency, or both. In a further example, an RP corresponds to a givenbandwidth part (BWP) such that the resources in the RP are confined tothe frequency range of the BWP. In yet a further example, the given BWPis associated with a given numerology (e.g., a numerology having asubcarrier spacing of 15 kHz, 30, kHz, etc.) such that the resources ofthe RP are defined by the given numerology.

A UE may be configured to use one or more specified resource pools.Then, the SL resource configuration takes place within the resourcepool(s) configured for the UE. These variations are applicable to any ofthe embodiments described herein.

In addition to providing new modes for grant-free SL transmission, otherembodiments of the present disclosure may also further enhance otherknown modes of SL transmission.

For example, in a first conventional mode of SL transmission, such asLTE-V2X mode 3 or NR-V2X mode 1, a base station schedules SL resource(s)to be used by a UE for SL transmission(s). Aspects of the presentdisclosure can be used to enhance this first conventional SLtransmission mode in order to add grant-free capabilities.

In this first conventional SL transmission mode, a DCI indicates a timedomain transmission pattern bitmap for UEs to determine resources to usefor an SL transmission. These SL transmission resources may be scheduleddynamically or semi-persistently; however, scheduling of the SLtransmission resources by the BS results in latency. Before the UE cantransmit on the SL, it must wait for the DCI from the BS. Furthermore,the dynamic nature of the resource scheduling increases the signalingoverhead associated with an SL transmission. Embodiments of the presentdisclosure may be used to allow SL transmission resource(s) and/or SLtransmission configuration(s) to be indicated via RRC, in order toovercome at least some of the disadvantages of fully dynamic orsemi-persistent scheduling via DCI.

More particularly, embodiments of the present disclosure provide methodsand apparatuses for a UE to independently select and/or adjust SLtransmission resources that have been previously preconfigured orconfigured via RRC.

In yet a further embodiment of the present disclosure used to enhancethe first conventional SL transmission mode, the UE can alsoindependently and dynamically select between different grant-free SLconfigurations. For example, a first grant-free SL configuration maycomprise configuration parameters that are advantageous in one type ofscenario or environment (traffic type, packet size, service type, QoS,etc.), yet disadvantageous in another. Whereas a second grant-free SLconfiguration may comprise configuration parameters that advantageous inthe another type of scenario or environment. Accordingly, enabling theUE to independently and dynamically select between different grant-freeSL configurations will improve SL transmission performance.

In a further embodiment, DCI may be used to update the SL transmissionresources that were previously configured in any of the aboveembodiments.

For another example, in second conventional mode of SL transmission,such as LTE-V2X mode 4 or NR-V2X mode 2, the UE autonomously determines,or otherwise determines without base station scheduling, SL transmissionresource(s) within SL resources that have been pre-configured orpreviously configured by the base station.

However, in the second conventional mode, while autonomously selectingresources within an RP improves latency, it also increases chances of amessage collision caused by UEs independently selecting the sameresource. When this happens, the collision may cause reliability issuesfor the message, which may not be successfully decoded by the intendedreceivers. Therefore, embodiments of the present disclosure providemethods and apparatuses to overcome at least some of the disadvantagesassociated with this second conventional mode of SL transmission.

More particularly, in some embodiments according to methods forselecting grant-free transmission resources based on decoding of SCIdescribed above, a first UE assists sidelink resource selection for oneor more second UEs. The first UE may transmit some information to thesecond UE in order to assist sidelink resource allocation. Suchinformation can correspond to sensing or interference measurements. Insome embodiments, a transmitting UE may assist a receiving UE byindicating resources for feedback in unicast or groupcast operation. Insome embodiments a UE can assist other UEs in the selection ofrepetition patterns in order to avoid resource collisions. For example,an indication message on grant free resource reservation or transmissionpattern selection can be transmitted to other UEs to improve thereliability for sidelink grant free transmission mode.

In further embodiments for enhancing the second conventional SLtransmission mode, a UE is configured/preconfigured with one or more SLtransmission configurations.

In particular, this can be achieved in a grant-free transmission mode,by configuring/preconfiguring a pool of two-dimensional time/frequencyrepetition patterns (e.g., as described above). The transmissionpatterns indicate the time and frequency location of each repetition ofa TB. The configuration/preconfiguration takes into account the UE needsand the radio conditions. The pattern selection is performed at leastonce within the periodicity of the configured/preconfigured grantresources.

In a further embodiment, DCI may be used to update the SL transmissionresources that were previously configured in any of the aboveembodiments.

In order to alleviate the half-duplex constraint, the pool ofconfigured/preconfigured transmission patterns should be such that anytwo distinct patterns should not collide in at least one time unit whichachieves the following benefits:

Due to near-far effects and in-band emissions, simultaneous PSSCHtransmissions from multiple UEs may interfere with each other eventhough those transmissions take place on different resources in thefrequency domain. Such detrimental impacts are avoided as long as thosedevices select different patterns.

A UE is not able to transmit and receive PSSCH simultaneously.Grant-free transmissions using the pattern pool allows UEs to transmitPSSCH and receive PSSCH from multiple UEs as long as those transmissionsare carried out using distinct patterns.

Out-Of-Coverage Operation

In some embodiments, an out-of-coverage UE can be pre-configured with atime-frequency repetition pattern and use this pattern to transmit aPSSCH in a grant-free manner. More generally, a UE may be configured orpre-configured with a pattern pool, autonomously select a pattern fromthe pool and use it to transmit a non-scheduled PSSCH. In this way, iftwo UEs share the same resources and transmit data simultaneously, thentheir transmission can still be resolved by virtue of using differentpatterns. The pattern pool solution could be applied for bothin-coverage and out-of-coverage scenarios.

FIG. 18C shows another example of a pattern pool. This pattern focuseson the time-domain multiplexing aspect in order to illustrate howpatterns can help overcome the half-duplex constraint which isespecially useful in multicast scenarios where several UEs need totransmit and receive data from each other simultaneously. In the exampleat hand, it can be seen that all 21UEs can transmit and receive datato/from each other which allows for mutual broadcast within the groupwhile overcoming the half-duplex constraint. As can be seen, fastretransmission of a TB is enabled by the proposed grant-freetransmission scheme which should be beneficial in terms of both latencyand reliability.

How many repetitions are allowed per patterns may depend on thetime-domain length of these patterns as well as the number of UEs. Onthe other hand, the length of the pattern in time-domain along with thesubcarrier spacing should fit within the periodicity of the configuredgrant resources which will dictate the overall latency of the scheme.Therefore, there is a tradeoff to be achieved in terms of latency andreliability, which depends on the subcarrier spacing and time-domainlength of the patterns. In general, with large subcarrier spacing suchas 60 kHz, there is more opportunity for long enough transmissionpatterns within a given latency constraint.

In-Coverage Operation

For a first method of grant-free in-coverage operation, the network mayassign patterns to the UEs so as to avoid collisions between VUEs andachieve the best latency/reliability tradeoff. For another method ofgrant-free in-coverage operation, the grant-free operation mechanism canbe similar to the out-of-coverage operation described in the abovesubsection with the caveat that the network can reconfigure commonpattern pool via SIB or dedicated pattern pool or pattern via RRC.

In some embodiments for out-of-coverage UEs, the UE pattern pool ispre-configured and/or the UE pattern pool is UE-specific.

Sensing and Resource Selection

If the UE is configured/preconfigured with a UE-specific pattern, nosensing or resource selection may be needed.

If the UE is configured/preconfigured with pattern pools, a patternselection is needed. As discussed earlier, sensing may enhance theperformance of pattern selection for UEs that areconfigured/preconfigured with pattern pools.

In some embodiments, sharing of the configured/pre-configured SLtransmission resources with UEs not configured or pre-configured withgrat free SL transmission resources is not precluded. For example, whenunder network coverage, it is up to gNB implementation whether toschedule users on the configured resources for SL grant freetransmissions. Similarly, the configured resources SL grant freeresources can also be shared with other UEs not scheduled thatautonomously determine resources for SL transmission without networkinvolvement. In some embodiments, a UE configured/preconfigured with agrant free SL transmission resource(s), such as a transmission pattern,may have to share some of the resources with another UE that isoperating under a non-grant-free mode of operation. In this case, someembodiments will prioritize the UE configured/preconfigured with thegrant free SL transmission resource(s) over the non-grant-free UEbecause this grant-free SL transmission targets to achieve low latencyand high reliability QoS of advanced NR-V2X use cases.

In an embodiment of the present disclosure where a NR-V2X mode-2 UE isenhanced to provide grant-free SL transmissions, if the UE ispre-configured with a UE-specific pattern and then is reconfigured bythe network with a dedicated pattern when it is in-coverage, then the UEbehaves essentially as a NR-V2X mode-1 UE configured with the samepattern.

On the other hand, if a NR-V2X mode-2 UE is pre-configured with apattern pool and is then reconfigured by the network with a common ordedicated pattern pool, it will essentially behave as a NR-V2X mode-2 UEin coverage with respect to pattern selection from the pattern pool.

According to yet another embodiment of the present disclosure, a firstUE may schedule sidelink transmissions of other UEs. For example, thefirst UE may implement any of the above methods described above, inplace of a base station. This embodiment can be useful for anout-of-coverage scenario where a UE, perhaps having more capability thanother UEs around it, can perform scheduling functions on behalf of thebase station. In some embodiments, the base station designates thescheduling UEs within a group of users that are out-of-coverage. In someembodiments, the type of UE scheduling may be dynamic or throughconfigured grant (e.g., grant-free). In some embodiments, an in-coverageUE can receive a configuration signaling (e.g. RRC signaling) from thebase station and forward the configuration signaling through unicast,multicast or broadcast to one or more UEs in its proximity. Theconfiguration signaling can correspond to a specific SL resourcetransmission pattern or a pool of transmission patterns. Theconfiguration signaling may also correspond to one or multiple SL grantfree configuration or pre-configurations. In some other embodiment, a UEcan coordinate the transmission patterns among a group of UEs that areout of network coverage. Coordinating may involve assigning a specifictransmission pattern to each UE in the group in a way that minimizescollisions between SL transmissions of different UEs in the group.

Pattern and Pattern Pool Design

UE can be configured with a pattern or select a pattern among a patternpool for SL transmissions as discussed throughout this disclosure. Thepattern pool can follow a design as described in FIG. 1K where for aresource grid with n frequency resource and n+1 time resources, aK=n*(n+1)/2, where n=4, pattern can be created such that if K users aretransmitting each other, they can at least receive one transmission ofevery other users and no collision on the signal happens. However, insome cases, the number of frequency resources may be not enough tocreate such pattern without collision. In this case, some frequencyoverlap between different UEs may be allowed for designing the pattern.However, different UEs can still have at least one transmissionoccupying a different time resource than any other UEs that select orassigned one pattern. An example is show in FIG. 18D, where we have 3frequency resources and 10 time resources, 10*(10−1)/2=45 patterns canbe created. Three UEs may occupy one time-frequency resource in onetransmission among their corresponding patterns, but no two UEs willcollide on both transmissions as at least one transmission will occupydifferent time resource.

Selection of Resources Based on UE ID

When UE autonomously select a transmission resource or a transmissionpattern or a time frequency resource pattern (TFRP) among a resourcepool or transmission pattern pool. A UE may select a resource based onsome form of UE ID. The UE ID can be a higher layer UE ID, a MAC ID, aradio network temper identifier (RNTI), a connection ID or any ID thatmay differentiate the UE with another UE. The ID may be preconfigured orconfigured by the gNB or the network. UE may select the pattern based ona function of their UE ID. As an example in FIG. 1K, UE may derive theirpattern based on pattern ID=(UE ID) mod(total number of patterns in thepool), where mod is a modulo operation and the total number of patternsis 10. And use the pattern ID to map the UE number shown in the figurefor the selected pattern.

System Level Simulation of Different Resource Allocation Schemes

Simulations comparing an embodiment of the present disclosure (Mode 2-c)with a conventional sensing and reservation based UE autonomousselection scheme (Mode 2-a) are presented in FIGS. 23-26. Packetreception rate (PRR) and packet inter-reception (PIR) performance areused for performance evaluation. The simulation assumptions andparameters are described in Table 1 below.

TABLE 1 Simulation Assumptions Parameter Assumption Layout Highwayscenario UE distribution UE drop A Frequency 6 GHz Simulation bandwidth100 MHz In-band emission According to TR 36.885 evaluation assumptions,with {W, X, Y, Z} = {3, 6, 3, 3} Link type Direct vehicle-to-vehiclelink VUE antenna model TR 37.885 Option 1 Traffic Model TR 37.885Periodic Model 2 or Aperiodic Model 1

Significant gains in terms of PRR for both single transmission andrepetition are evident. The PIR results follow the same trend as PRR inall cases.

Numerous modifications and variations of the present disclosure arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced otherwise than as specifically described herein.

What is claimed is:
 1. A method performed by a user equipment (UE), themethod comprising: transmitting, by a UE, sidelink (SL) controlinformation comprising a scheduling assignment (SA) indicating an SLtransmission resource for a SL data transmission to a target UE, the SLtransmission resource based on one or more occupied SL resourcesidentified by the UE, and the SL transmission resource includingresources for an initial transmission and one or more retransmissions;and transmitting, by the UE, the SL data transmission using the SLtransmission resource according to the transmitted SL controlinformation, wherein the SL control information and the SL datacommunication are transmitted by the UE without receiving, in a downlinkcontrol information (DCI), a grant of communication resources.
 2. Themethod of claim 1, further comprising sensing a SL transmissioninvolving another UE to identify the one or more occupied SL resources.3. The method of claim 2, wherein sensing the SL transmission involvingthe another UE comprises decoding a sidelink control channel transmittedby the another UE to identify a transmission resource scheduled for theanother UE.
 4. The method of claim 3, wherein decoding the SL controlchannel transmitted by the another UE comprises decoding one or acombination of: a scheduling assignment; a side link control information(SCI); and a physical sidelink control channel (PSCCH).
 5. The method ofclaim 3, further comprising selecting the SL transmission resource byavoiding selecting the transmission resource scheduled for the anotherUE.
 6. The method of claim 5, wherein the same resources are selectedfor the initial transmission and the one or more retransmissions.
 7. Themethod of claim 3, wherein the SL transmission resource comprises a SLtransmission pattern, the transmission resource scheduled for theanother UE comprises a transmission pattern scheduled for the anotherUE, and avoiding selecting the transmission resource scheduled for theanother UE comprises avoiding the transmission pattern scheduled for theanother UE.
 8. The method of claim 2, wherein sensing the SLtransmission involving the another UE comprises measuring SLtransmission resources.
 9. The method of claim 8, wherein measuring SLtransmission resources comprises measuring physical sidelink sharedchannel (PSSCH) resources indicated or reserved for transmission by asidelink control information transmitted by the another UE.
 10. Themethod of claim 1, wherein the initial transmission and the one or moreretransmissions correspond to a same transport block or differenttransport blocks.
 11. A user equipment (UE) comprising: a processor; anda non-transitory computer readable storage medium storing programmingfor execution by the processor, the programming including instructionsfor: transmitting, by a UE, sidelink (SL) control information comprisinga scheduling assignment (SA) indicating an SL transmission resource fora SL data transmission to a target UE, the SL transmission resourcebased on one or more occupied SL resources identified by the UE, and theSL transmission resource including resources for an initial transmissionand one or more retransmissions; and transmitting, by the UE, the SLdata transmission using the SL transmission resource according to thetransmitted SL control information, wherein the SL control informationand the SL data communication are transmitted by the UE withoutreceiving, in a downlink control information (DCI), a grant ofcommunication resources.
 12. The UE of claim 11, wherein the programmingfurther includes instructions for sensing a SL transmission involvinganother UE to identify the one or more occupied SL resources.
 13. The UEof claim 12, wherein sensing the SL transmission involving the anotherUE comprises decoding a sidelink control channel transmitted by theanother UE to identify a transmission resource scheduled for the anotherUE.
 14. The UE of claim 13, wherein decoding the SL control channeltransmitted by the another UE comprises decoding one or a combinationof: a scheduling assignment; a side link control information (SCI); anda physical sidelink control channel (PSCCH).
 15. The UE of claim 13,wherein the programming further includes instructions for selecting theSL transmission resource by avoiding selecting the transmission resourcescheduled for the another UE.
 16. The method of claim 15, wherein thesame resources are selected for the initial transmission and the one ormore retransmissions.
 17. The UE of claim 13, wherein the SLtransmission resource comprises a SL transmission pattern, thetransmission resource scheduled for the another UE comprises atransmission pattern scheduled for the another UE, and avoidingselecting the transmission resource scheduled for the another UEcomprises avoiding the transmission pattern scheduled for the anotherUE.
 18. The UE of claim 12, wherein the SL transmission involving theanother UE comprises measuring SL transmission resources.
 19. The UE ofclaim 18, wherein measuring SL transmission resources comprisesmeasuring physical sidelink shared channel (PSSCH) resources indicatedor reserved for transmission by a sidelink control informationtransmitted by the another UE.
 20. The UE of claim 11, wherein theinitial transmission and the one or more retransmissions correspond to asame transport block or different transport blocks.